.NET Interoperability at a Glance 2 – Managed Code Interoperation

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See more Interoperability examples here.

Contents

Contents of this article:

  • Contents
  • Read also
  • Overview
  • Introduction
  • Forms of Interop
  • Managed Code Interop
  • Summary
  • Where to go next

Read also

More from this series:

Overview

In the previous article, you learnt what interoperability is and how it relates to the .NET Framework. In this article, we’re going to talk about the first form of interoperability, the Managed Code Interop. In the next article, we’ll talk about the other forms.

Introduction

So, to understand Interoperation well in the .NET Framework, you must see it in action. In this article, we’ll talk about the first form of .NET interoperability and see how to implement it using the available tools.

Just a reminder, Interoperability is the process of communication between two separate systems. In .NET Interop, the first system is always the .NET Framework; the other system might be any other technology.

Forms of Interop

Interoperability in .NET Framework has two forms:

  • Managed Code Interoperability
  • Unmanaged Code Interoperability

Next, we have a short discussion of each of the forms.

Managed Code Interop

This was one of the main goals of .NET Framework. Managed Code Interoperability means that you can easily communicate with any other .NET assembly no matter what language used to build that assembly.

Not surprisingly, because of the nature of .NET Framework and its runtime engine (the CLR,) .NET code supposed to be called Managed Code, while any other code is  unmanaged.

To see this in action, let’s try this:

  1. Create a new Console application in the language you like (C#/VB.NET.)
  2. Add a new Class Library project to the solution and choose another language other than the one used in the first project.
  3. In the Class Library project, add the following code (choose the suitable project):
    // C#
    
    public static class Hello
    {
        public static string SayHello(string name)
        {
            return "Hello, " + name;
        }
    }
    ' VB.NET
    
    Public Module Hello
        Public Function SayHello(ByVal name As String) As String
            Return "Hello, " & name
        End Function
    End Module
  4. Now, go back to the Console application. Our goal is to call the function we have added to the other project. To do this, you must first add a reference to the library in the first project. Right-click the Console project in Solution Explorer and choose Add Reference to open the Add Reference dialog (figure 1.) Go to the Projects tab and select the class library project to add it.

    Figure 1 - Add Reference to a friend project

    Figure 1 - Add Reference to a friend project

  5. Now you can add the following code to the Console application to call the SayHello() function of the class library.
    // C#
    
    static void Main()
    {
        Console.WriteLine(ClassLibrary1.Hello.SayHello("Mohammad Elsheimy"));
    }
    ' VB.NET
    
    Sub Main()
        Console.WriteLine(ClassLibrary1.Hello.SayHello("Mohammad Elsheimy"))
    End Sub

How this happened? How could we use the VB.NET module in C# which is not available there (or the C#’s static class in VB which is not available there too)?

Not just that, but you can inherit C# classes from VB.NET (and vice versa) and do all you like as if both were created using the same language. The secret behind this is the Common Intermediate Language (CIL.)

When you compile your project, the compiler actually doesn’t convert your C#/VB.NET code to instructions in the Machine language. Rather, it converts your code to another language of the .NET Framework, which is the Common Intermediate Language. The Common Intermediate Language, or simply CIL, is the main language of .NET Framework which inherits all the functionalities of the framework, and which all other .NET languages when compiled are converted to it.

So, the CIL fits as a middle layer between your .NET language and the machine language. When you compile your project, the compiler converts your code to CIL statements and emits them in assembly file. In runtime, the compiler reads the CIL from the assembly and converts them to machine-readable statements.

How CIL helps in interoperation? The communication between .NET assemblies is now done through the CIL of the assemblies. Therefore, you don’t need to be aware of structures and statements that are not available in your language since every statement for any .NET language has a counterpart in IL. For example, both the C# static class and VB.NET module convert to CIL static abstract class (see figure 2.)

Figure 2 - CIL and other .NET languages

Figure 2 - CIL and other .NET languages

Managed Interop is not restricted to C# and VB.NET only; it’s about all languages run inside the CLR (i.e. based on .NET Framework.)

If we have a sneak look at the CIL generated from the Hello class which is nearly the same from both VB.NET and C#, we would see the following code:

.class public abstract auto ansi sealed beforefieldinit ClassLibrary1.Hello
       extends [mscorlib]System.Object
{

    .method public hidebysig static string  SayHello(string name) cil managed
    {
      // Code size       12 (0xc)
      .maxstack  8
      IL_0000:  ldstr      "Hello, "
      IL_0005:  ldarg.0
      IL_0006:  call       string [mscorlib]System.String::Concat(string,
                                                              string)
      IL_000b:  ret
    } // end of method Hello::SayHello

} // end of class ClassLibrary1.Hello

On the other hand, this is the code generated from the Main function (which is also the same from VB.NET/C#):

.class public abstract auto ansi sealed beforefieldinit ConsoleApplication1.Program
       extends [mscorlib]System.Object
{

    .method private hidebysig static void  Main() cil managed
    {
      .entrypoint
      .maxstack  8
      IL_0000:  ldstr      "Mohammad Elsheimy"
      IL_0005:  call       string [ClassLibrary1]ClassLibrary1.Hello::SayHello(string)
      IL_000a:  call       void [mscorlib]System.Console::WriteLine(string)
      IL_000f:  ret
    } // end of method Program::Main

} // end of class ConsoleApplication1.Program

You can use the ILDasm.exe tool to get the CIL code of an assembly. This tool is located in Program FilesMicrosoft SDKsWindows<version>bin.

Here comes a question, is there CIL developers? Could we write the CIL directly and build it into .NET assembly? Why we can’t find much (if not any) CIL developers? You can extract the answer from the CIL code itself. As you see, CIL is not so friendly and its statements are not so clear. Plus, if we could use common languages to generate the CIL, we we’d like to program in CIL directly? So it’s better to leave the CIL for the compiler.

Now, let’s see the other form of .NET interoperation, Unmanaged Code Interoperability.

Summary

So, the secret of Managed Code Interoperation falls in the Common Intermediate Language or CIL. When you compile your code, the compiler converts your C#/VB.NET (or any other .NET language) to CIL instructions and saves them in the assembly, and that’s the secret. The linking between .NET assemblies of different languages relies on the fact that the linking is actually done between CILs of the assemblies. The assembly code doesn’t (usually) have any clue about the language used to develop it. In the runtime, the compiler reads those instructions and converts them to machine instructions and execute them.

Next, we’ll talk about the other form of .NET Interoperation, it’s the interoperation with unmanaged code.

Where to go next

Read more about Interoperability here.

More from this series:

.NET Interoperability at a Glance 1 – Introduction

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See more Interoperability examples here.

Contents

Contents of this article:

  • Contents
  • Read also
  • Overview
  • Introduction
  • Summary
  • Where to go next

Read also

More from this series:

Overview

.Net Framework Logo
Image via Wikipedia

In this article and the few following it, we’ll try to take a tour in Interoperability in .NET Framework.

In this lesson, we’ll start by an introduction to the concept of Interoperability. In the next few lessons, we’ll have a look at Interoperability and how it fits into the .NET Framework and other technologies.

Since Interoperability is a very huge topic and cannot be covered in just a few articles, we’ll concentrate on Interoperability in .NET Framework (not any other technologies) and summarize its uses.

Here we go!

Introduction

Let’s get hands on the concept of Interoperability and it’s relation to the .NET Framework.

Concept

Interoperability (reduced to Interop) is the ability of two diverse systems or different systems to communicate (i.e. inter-operate) with each other. When I say ‘two systems’ I assume that the first one is always the .NET Framework, since we are interested in .NET and also the interoperability is a very huge topic and cannot be summarized in just a few articles. The other system might be any other software, component, or service based on any technology other than the .NET Framework. For example, we could interoperate with Win32 API, MFC applications, COM/ActiveX components, and so on.

So we have two different systems, the first is the .NET Framework, while the other is any other technology. Our goal is to communicate with that stranger; that’s the main goal of Interoperability in .NET Framework.

Goals and Benefits

Here comes a question (or a few questions!), why do I need interoperation? Why I do need to communicate with other systems at all? If I need specific features, couldn’t I just use existing functionalities of .NET Framework to accomplish my tasks? I can even redevelop them!

We can summarize the answer of those questions in a few points:

  • First, in many cases, you can’t redevelop those components because the functionalities they offer is either very difficult (sometimes impossible) or maybe you don’t sufficient knowledge to redevelop them! Unless if you are very brilliant and have enough knowledge of the Assembly language, you can develop your API that would replace current system API, and then you’ll have also to interoperate with your API to be able to call it from your .NET Framework application.
  • If you’re not convinced yet, this is should be for you. You might be not having enough time to redevelop the component that may take a very long time and effort to complete. Imagine how much time would take to code, debug, and test your component. Plus, you can rely on existing components and trust them, many bugs can appear in your code from time to time and you’ll have to fix them all!
  • Other 3rd party component might not exist, or maybe the company you work for require you to use such those components.
  • You don’t need to reinvent the wheel, do you?

So, including Interop code in your .NET projects is sometimes inevitable (especially when working with Windows API) that you definitely can’t keep yourself away from them.

Summary

So you have now basic understanding of what Interoperability means. As a reminder, Interoperability is the process of two diverse systems communicate with each other. For us, the first system is the .NET Framework. The other system is any other technology (Windows API, MFC, COM/ActiveX, etc.)

You can’t live without Interop, actually you did some interoperation in your work (you may be actually do that every day.)

Now you are ready to take a look at how Interop fits in .NET Framework.

Where to go next

Read more about Interoperability here.

More from this series:

Consuming URL Shortening Services – X.co

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Read more about URL shortening services here.

Source- Elsheimy.Samples.ShortenSvcs.zip

Contents

Contents of this article:

  • Contents
  • Overview
  • Introduction
  • API
  • WCF Services
    • Squeeze Service
    • Reporting Service
  • RESTful Services
    • Squeeze Service
    • Reporting Service
  • Source Code
  • What’s next

Overview

This is another article of our URL shortening services series. This article is talking about X.co shortening service provided by Go Daddy. If you don’t know how to access this service from your .NET application, then it’s the time to.

We’ll have a complete discussion of the WCF services offered by X.co. Then, we’ll consider the RESTful interfaces provided.

Introduction

Today we are going to talk about one of the most popular URL shortening services on the web now; it’s the new X.co provided by Go Daddy, the dominating domain names and web hosting service provider.

While X.co is considered very new since it has released just few months ago, it gained support from users worldwide very quickly, and now it’s one of the most popular shortening services exist in the web. Although the interface provided to users doesn’t offer great functionality, the API interface it provides really deserves respect since it’s one of the most easiest yet powerful APIs (for shortening services) exist on the web now.

API

The most noticeable thing about X.co API is that unlike other APIs it’s based on ASP.NET and WCF (WOW!) Moreover, the WCF service provides you a RESTful interface. Thus, you end up with two interfaces, one is based on WCF, and other is a REST web service.

You might not be familiar with WCF or other new technologies related to versions higher than .NET 2.0, don’t worry it’s just a matter of names! You use WCF services the same way as with ordinary Web Services.

In this writing, we’ll first talk about WCF/Web service interfaces provided to you by X.co. After that, we’ll have a look at how RESTful interfaces fit in the picture.

Before we begin our discussion, you’ll need to grab your API key that’s required by all functions for authentication. To get your API key, first create a free account at http://www.godaddy.com if you don’t have one yet. Figure 1 shows the registration page.

Figure 1 - Go Daddy Registration Page

After you complete the registration process, go to http://x.co, login with your username and password, and go to Settings to get your API key. See figure 2.

Figure 2 - X.co API Key

Notice that this is a secret key and you should keep it away from intruder eyes. This key will be used in all of your work with X.co API.

WCF Services

WCF or Web services, not a big deal, let’s just call it WCF. Our service X.co provides you two WCF services that you can access:

The Squeeze service supports only one function that can be used to shorten (squeeze) long URLs. In fact, the Squeeze service provides other functions too, however, they are either deprecated or for the internal use of Go Daddy. The other service, the Reporting service, supports functions related to reports and analytics of short URLs (like clicks and referrer sites.)

Whatever service you like to use, you must reference it to your projects. To add a reference to a web service to your project, you can use one of two ways. The first and better way is to use Visual Studio. Right-click the Web References node under your project node in Solution Explorer and select Add Web Reference to launch the Add Web Reference dialog (see figure 3.)

Figure 3 - Solution Explorer - Add Web Reference

Figure 3 - Solution Explorer - Add Web Reference

The Add Web Reference dialog is now on the top of the IDE, the dialog might appear different in .NET 2.0 than higher versions (see figure 4 and figure 5.) Whatever, write the address of the service that you need to add, click Go so can Visual Studio read service description, write a good name in the Reference Name field that would be the namespace that groups service objects, and finally click Add Reference. Notice that we have used the name xcoapi for the Squeeze service, and xcoapirpt for the Reporting service.

Figure 4 - Add Web Reference Dialog in .NET 3.0+

Figure 4 - Add Web Reference Dialog in .NET 3.0+

Figure 5 - Add Web Reference Dialog in .NET 2.0

Figure 5 - Add Web Reference Dialog in .NET 2.0

Another approach to get the required source files for the service is to use the svcutil.exe tool that’s used internally by Visual Studio. This is a command tool that generates source files for web and WCF services. You can use this tool as follows:

svcutil.exe http://api.x.co/Squeeze.svc?wsdl /language=C#
svcutil.exe http://api.x.co/Squeeze.svc?wsdl /language=VB

Notice that we have included the address of the discovery (description) WSDL data of the services so that the tool can read it. Remember to select your language in the command.

Squeeze Service

The first function we have today and the only function of the Squeeze service (http://api.x.co/Squeeze.svc) is the Shorten() function that’s used to shorten long URL files. This function simply accepts 2 arguments:

  • url:
    The long URL to be shortened.
  • apiKey:
    The API key used to authenticate the call.

There’re other functions existing in the Squeeze service but they are either deprecated or reserved for internal use by Go Daddy.

After you ensure that a reference of the service is added to your project (check the previous section) you can start writing your code. The following function accepts the long URL and returned the shortened one that’s -at the time of this writing- is no more than 16 characters (e.g. http://x.co/8Gg8):

// C#

string Shorten(string url, string apiKey)
{
    using (xcoapi.Squeeze sq = new xcoapi.Squeeze())
    {
        return sq.Shorten(url, apiKey);
    }
}

Notice that web services consumes lots of system resources and you should release them as soon as you finish you work with them, that’s why we have used the C# using statement.

Reporting Service

The other service we have is the Reporting service (http://api.x.co/Reporting.svc) that offers you great deal of analytics and reporting functionalities that can be sorted in 3 areas:

  • Click count (the number of uses of the short URL)
  • Referrer sites (for the short URL)
  • Uses by locations (city, region, and country.)

This service supports 5 functions:

  • GetTotalMapClick():
    Returns total clicks (uses) of a short URLs.
  • GetMapClicksByDates():
    Returns clicks of a short URL made within a given time period grouped by days.
  • GetMapClicksByHour():
    Returns clicks of a short URL made today grouped by hours.
  • GetMapReferrersByDates():
    Returns referrer links made to the short URL within a given time period grouped by days.
  • GetMapLocationsByDates():
    Returns clicks of a short URL made within a given time period grouped by geographic location.

Those five functions are very similar in many ways. First, they all accept two required parameters:

In addition, the last four functions work the same way. They all return arrays of objects. GetMapClicksByHour() for instance returns the number of clicks made today grouped by hours each hour is represented by an object that contain the hour number besides the clicks made in that hour, and all objects are grouped inside one array.

The other functions GetMapClicksByDates(), GetMapReferrersByDates(), and GetMapLocationsByDates() work the same way and accept the same parameters except that they accept four additional parameters represent the begin and the end dates of the time period and whether the date parameters were set or leaved empty.

How can the four parameters help? You can define both and set the two flags to indicate that we need a specific time period. You can also set one of them and set its flag to indicate that you need to start from a specific day and get analytics till now. Notice that you can’t leave both empty.

The following code returns the total number of clicks for a specific short URL:

// C#

int GetTotalClicks(string shortCode, string apiKey)
{
    using (xcoapirpt.ReportingClient rpt = new xcoapirpt.ReportingClient())
    {
        return rep.GetTotalMapClick(apiKey, shortCode);
    }
}

And the following code is the same as the above except that it uses .NET 2.0:

// C#

int GetTotalClicks(string shortCode, string apiKey)
{
    using (xcoapirpt.Reporting rpt = new xcoapirpt.Reporting())
    {
        int totalClicks;
        bool succeeded;
        rep.GetTotalMapClick(apiKey, shortCode, out totalClicks, out succeeded);

        return succeeded ? totalClicks : -1;
    }
}

Notice the slight difference between the two calls (in .NET 2.0 and higher versions.) In .NET 2.0, the returned value is specified as an output parameter.

The following code is somewhat complex than the previous. The following code returns the refer links for our short URL:

// C#

xcoapirpt.ReferrerEventInfo[] GetReferrers
    (string shortUrl, string apiKey, out int totalClicks)
{
    using (xcoapirpt.Reporting rep = new xcoapirpt.Reporting())
    {
        xcoapirpt.ReferrerEventInfo[] results =
            rep.GetMapReferrersByDates(apiKey, shortUrl,
                DateTime.Now - new TimeSpan(7, 0, 0, 0, 0), true, DateTime.Now, true);

        totalClicks = 0;
        foreach (xcoapirpt.ReferrerEventInfo r in results)
            totalClicks += r.TotalSpecified ? r.Total : 0;

        return results;
    }
}

Notice how we specify the start and end date parameters and their flags to get only the last week analytics. Notice also the type of the array returned from the function and how we used it to get the required information.

RESTful Services

If you prefer not to use the WCF services, you can start with the REST interface provided to you by the kind-hearted WCF services. A RESTful service is simply a group of related web functions that has specific formats; some of return plaint text, some return XML data, and others return JSON.

Keep in mind that WCF services are supported natively by .NET framework and thus they are faster and easier to work with.

Squeeze Service

Not surprisingly, our RESTful Squeeze service is provided to us by the address http://api.x.co/Squeeze.svc. This service has two functions to shorten URLs, one is JSON, and the other is plain text.

The first function that returns plain text can be called using the following address:

http://api.x.co/Squeeze.svc/text/{apiKey}?url={url}

Now you have the address and ready with the input, the following function calls the previous function to shorten long URLs:

// C#

string Shorten(string url, string apiKey)
{
    WebRequest req = HttpWebRequest.Create(
        string.Format("http://api.x.co/Squeeze.svc/text/{0}?url={1}",
        apiKey, url));

    req.Timeout = 10000; // 10 seconds

    string shortUrl;
    System.IO.Stream stm;

    stm = req.GetResponse().GetResponseStream();

    using (System.IO.StreamReader rdr = new System.IO.StreamReader(stm))
    {
        return rdr.ReadToEnd();
    }
}

Reporting Service

Likewise, the Reporting service has the following address: http://api.x.co/Squeeze.svc. This service provides you with many functions like its WCF counterpart, however, all of them are JSON expect one is plain text. Because JSON is not natively supported by .NET Framework and thus requires the use of other 3rd party components (e.g. Json.NET) we won’t consider those endpoints. However, we have our total clicks function that returns plain text:

// C#

int GetTotalClicks(string shortCode, string apiKey)
{
    WebRequest req = HttpWebRequest.Create(
        string.Format("http://x.co/Reporting.svc/map/{0}/{1}/total",
        apiKey, shortCode));

    req.Timeout = 10000; // 10 seconds

    System.IO.Stream stm;

    stm = req.GetResponse().GetResponseStream();

    using (System.IO.StreamReader rdr = new System.IO.StreamReader(stm))
    {
        return int.Parse(rdr.ReadToEnd());
    }
}

Again, the short code is the only required piece of the short URL, you do not need to include the http://x.co/ (actually, you can’t!)

Source Code

Download the source code files from here.

What’s next

Consider reading more about URL shortening services here.

Understanding Value Types and Reference Types

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Contents

Contents of this article:

  • Contents
  • Introduction
  • Passing Mechanism
  • The Two Genres
  • Value Types
  • Reference Types
  • Boxing and Unboxing
    • Manual Boxing
    • Manual Unboxing
    • Automatic Boxing
    • Automatic Unboxing
  • Summary

Introduction

Today, we’ll have a brief discussion of value types and reference types in .NET framework and how their behavior change while used or passed to functions. We’ll talk about the passing mechanism, the two genres of .NET types, the scope, and the conversion routines between the two genres.

Passing Mechanism

When you pass an object to a function, this object can be passed either by value or by reference.

To pass an object by value means that a copy of the object is passed to the function not the object itself so changes to the object inside the function won’t affect your original copy.

On the other hand, passing an object by reference means passing that object itself so changes to the object inside that function is reflected on your original copy.

Consider the following example. Although the function changed the value of i, the change didn’t affect the original variable that’s because the variable is passed by value.

// C#

static void Main()
{
    int i = 10;
    int j = i;

    j = 5;

    // you expect '5'
    Console.WriteLine(i);
    // but i is still 10 !!

    // Now you try another way

    Sqr(i);

    // you expect '100'
    Console.WriteLine(i);
    // but i is still 10 !!!
}

static void Sqr(int i)
{
    i *= i;
}
' VB.NET

Sub Main()
    Dim i As Integer = 10
    Dim j As Integer = i

    j = 5

    ' you expect '5'
    Console.WriteLine(i)
    ' but i is still 10 !!!

    ' now you try another way

    Sqr(i)

    ' you expect '100'
    Console.WriteLine(i)
    ' but i is still 10 !!!
End Sub

Sub Sqr(ByVal i As Integer)
    i = i * i
End Sub

Now, let’s try something else. The following example passes i by reference.

// C#

static void Main()
{
    int i = 10;

    Sqr(ref i);

    // you expect '100'
    Console.WriteLine(i);

    // you are right!
}

static void Sqr(ref int i)
{
    i *= i;
}
' VB.NET

Sub Main()
    Dim i As Integer = 10

    Sqr(i)

    ' you expect '100'
    Console.WriteLine(i)

    ' you are right!
End Sub

Sub Sqr(ByRef i As Integer)
    i = i * i
End Sub

Notice how the ref keyword in C# (ByRef in VB.NET) changed the overall behavior. Now, i itself is passed to our function, so the changes made in the function affected the original variable (both are the same.)

The Two Genres

Talking about passing object by value or by reference leads up to talk about the two major genres of types in .NET Framework:

  • Value Types
  • Reference Types

Value Types

Value types are those normally passed by value unless you explicitly specify the ref keyword (or ByVal in VB.NET) to override the default behavior and pass the object by reference.

Value types in .NET are those inherit -directly or indirectly- from System.ValueType including all structures, enumerations, and primitives (integers, floats, etc.)

The previous examples use an integer value that’s absolutely a value-type.

Value types are stored on the first section of the memory, the stack. Thus, they are removed from memory as soon as their scope ends. The scope marks the beginning and the end of object’s life (object is considered alive at the time you declare it.) See the following code the marks scopes inside a class.

// C#

class ClassScope
{
    // Scope 1

    void Method1()
    {
        // Scope 1.1

        {
            // Scope 1.1.1
            {
                // Scope 1.1.1.1
            }

            {
                // Scope 1.1.1.2
            }
        }
    }

    void Method2()
    {
        // Scope 1.2

        if (true)
        {
            // Scope 1.2.1

            while (true)
            {
                // Scope 1.2.1.1
            }
        }
    }
}
' VB.NET

Class ClassScope
    ' Scope 1

    Sub Method1()
        ' Scope 1.1
    End Sub

    Sub Method2()
        ' Scope 1.2

        If True Then
            ' Scope 1.2.1

            Do While True
                ' Scope 1.2.1.1
            Loop
        End If
    End Sub
End Class

Reference Types

Reference types are those normally passed by reference and never can be passed by value. Reference types include all objects other than value types, we mean all other classes inherit from System.Object -directly or indirectly- and don’t inherit from System.ValueType.

Reference types are stored in the other version of the memory, the heap, and you can’t determine when the object is removed from memory since the heap is fully managed by the memory manager of .NET, the GC (Garbage Collector.)

Now, let’s see the difference between value types and reference types in action. The following example instantiates two objects, one is a structure (value type) and the other is a class (reference types.) After that, both objects are passed to two functions, both try to change the contents of the objects. The changes of the function affect the reference type outside, while the other value type object outside the function doesn’t get affected.

// C#

static void Main()
{
    ValStruct valObj = new ValStruct();
    RefClass refObj = new RefClass();

    valObj.x = 4;
    valObj.y = 4;
    refObj.x = 4;
    refObj.y = 4;

    MultipleStruct(valObj);
    MultipleClass(refObj);

    Console.WriteLine("Struct:tx = {0},ty = {1}",
        valObj.x, valObj.y);

    Console.WriteLine("Class:tx = {0},ty = {1}",
        refObj.x, refObj.y);

    // Results
    // Struct:  x = 4,  y = 4
    // Class:   x = 8,  y = 8
}

static void MultipleStruct(ValStruct obj)
{
    obj.x *= 2;
    obj.y *= 2;
}

static void MultipleClass(RefClass obj)
{
    obj.x *= 2;
    obj.y *= 2;
}

struct ValStruct
{
    public int x;
    public int y;
}

class RefClass
{
    public int x;
    public int y;
}
' VB.NET

Sub Main()

    Dim valObj As New ValStruct()
    Dim refObj As New RefClass()

    valObj.x = 4
    valObj.y = 4
    refObj.x = 4
    refObj.y = 4

    MultipleStruct(valObj)
    MultipleClass(refObj)

    Console.WriteLine("Struct:tx = {0},ty = {1}", _
            valObj.x, valObj.y)

    Console.WriteLine("Class:tx = {0},ty = {1}", _
            refObj.x, refObj.y)

    ' Results
    ' Struct:  x = 4,  y = 4
    ' Class:   x = 8,  y = 8
End Sub

Sub MultipleStruct(ByVal obj As ValStruct)
    obj.x *= 2
    obj.y *= 2
End Sub

Sub MultipleClass(ByVal obj As RefClass)
    obj.x *= 2
    obj.y *= 2
End Sub

Structure ValStruct
    Public x As Integer
    Public y As Integer
End Structure

Class RefClass
    Public x As Integer
    Public y As Integer
End Class

A little yet very important note: When comparing objects with the double equal signs (or the single sign in VB.NET,) objects are being compared internally using the System.Object.Equals() function. This function returns True if both value objects have the same value or both reference objects refer to the same object (doesn’t matter if both have the same value and are different objects.) Conversely, using the not equals operator (!= in C# and <> in VB.NET) uses the same comparison function, however, it reverses its return value (True becomes False and vice versa.)

Boxing and Unboxing

Boxing is the process of converting a value type into reference type. Unboxing on the other hand is the process of converting that boxed value type to its original state. Boxing and unboxing can be done manually (by you) or automatically (by the runtime.) Let’s see this in action.

Manual Boxing

Consider the following code:

    // C#
    byte num = 25;
    object numObj = num;
    ' VB.NET
    Dim num As Byte = 25
    Dim numObj As Object = num

The last code simply converted a value type (the byte variable) into reference type by encapsulating it into a System.Object variable. Does that really involve that passing the System.Object would be done by reference? Absolutely! (Check it yourself!)

Manual Unboxing

Now you have a boxed byte, how can you retrieve it later, i.e., restore it back to be a value type? Consider the following code:

    // C#
    // Boxing
    byte num = 25;
    object numObj = num;
    // Unboxing
    byte anotherNum = (byte)numObj;
    'VB.NET
    'Boxing
    Dim num As Byte = 25
    Dim numObj As Object = num
    'Unboxing
    Dim anotherNum As Byte = CByte(numObj)

Beware not to try to convert a boxed value to another type not its original type.

Automatic Boxing

Boxing can be done automatically by the runtime if you tried to pass that value type to a function that accepts a System.Object not that value type.

// C#
static void Main()
{
    byte num = 25;

    // Automatic Boxing
    Foo (num);
}

static void Foo(object obj)
{
    Console.WriteLine(obj.GetType());
    Console.WriteLine(obj.ToString());
}
' VB.NET
Sub Main()
    Dim num As Byte = 25

    'Automatic Boxing
    Foo(num)
End Sub

Sub Foo(ByVal obj As Object)
    Console.WriteLine(obj.GetType)
    Console.WriteLine(obj.ToString)
End Sub

Automatic Unboxing

The runtime can automatically unbox a boxed value:

// C#
static void Main()
{
    // Automatic Boxing
    object num = 25;

    // Automatic Unboxing – not really works
    Foo(num);
}

static void Foo(byte obj)
{
    Console.WriteLine(obj.GetType());
    Console.WriteLine(obj.ToString());
}
' VB.NET
Sub Main()
    ' Automatic Boxing
    Dim num As Object = 25

    ' Automatic Unboxing - works
    Foo(num)
End Sub

Sub Foo(ByVal obj As Byte)
    Console.WriteLine(obj.GetType)
    Console.WriteLine(obj.ToString)
End Sub

The difference between C# and VB.NET in the last situation is that VB.NET allows automatic unboxing while C# doesn’t. (Theoretically, VB.NET allows automatic conversion between the vast majority of types, while C# lacks this feature.)

Summary

That was a brief discussion of value types and reference types in .NET Framework. Value types are those normally when passed to a function or copied, a copy of the value is used not the original value. Therefore, changes made to that copy don’t affect the original object.

On the other hand, reference types are those when passed to a function or copied, the object itself is used. Therefore, any changes made inside the function or to the copy do affect the original object (both are the same.)

Value types in .NET are all types inherit from System.ValueType including structures, enumerations, and primitives. All other classes don’t inherit from System.ValueType are reference types.

Boxing is the process of converting a value type to reference type. Unboxing is retrieving that boxed reference type back. To box a variable simple convert it to System.Object. To unbox it, convert it back to its original type. Boxing could also occur automatically when you pass a value type to a function that accepts System.Object not the type itself.

Consuming URL Shortening Services – bit.ly

هذه المقالة متوفرة أيضا باللغة العربية، اقرأها هنا.

Read more about URL shortening services here.

Source- Elsheimy.Samples.ShortenSvcs.zip

Contents

Contents of this article:

  • Contents
  • Overview
  • Introduction
  • API
    • Overview
    • Function Explanation
    • Shortening Function
    • Expanding Function
    • Validation Function
    • Stats Function
    • Lookup Function
    • Info Function
    • Authentication Function
  • JSON Support
    • Sample
    • Where to go next

    Overview

    This is a very hot article that you can’t leave without checking it first. This article is talking about the most popular and powerful URL shortening service ever, bit.ly.

    Today, we are going to talk about bit.ly API, its functions, and how you can access them from your .NET application.

    Don’t forget to download the sample code at the end of the article.

    Let’s go!

    Introduction

    Today we are going to talk about the most popular yet most powerful URL shortening service ever in the web. Yes you guessed, it is bit.ly.

    Of course this service is well-known enough and we don’t need to describe it or talk about its features, so we’ll dig into the API immediately.

    API

    Overview

    There’re few things that you should keep in mind about bit.ly API:

    • REST API:

    The bit.ly API is a REST web service; means that it’s a collection of HTTP endpoints each accessed by a simple address filled with arguments the function (endpoint) requires the way you fill up query strings of a web page. Actually, you don’t need to care about REST web services or HTTP endpoints; you just need to know how to call those functions (simply, to access those addresses programmatically.)

    Yet, the current and only version of the API is version 3 and that can be accessed using the following address:

    http://api.bit.ly/v3/%5Bfunction_name%5D?%5Bargs%5D

    Simply, substitute function_name with the name of the function you need to call, and replace args with function arguments.

    Notice that you can try any function by just typing the address into the browser and navigating to the results.

    • Functions:

    The API provides you with lots of functions that satisfy your application needs. The following list contains the functions available:

    • Shorten:
      Used to shorten a long URL.
    • Expand:
      Used to expand the URL; to get the original long URL from the short one.
    • Validate:
      Used to validate a username and his API key.
    • Clicks:
      Used to retrieve stats (number of clicks) about the short URL specified.
    • Lookup:
      Used to check a long URL if exists in the database, i.e., if it has been shortened before.
    • Info:
      Used to retrieve information about the URL (e.g. the user created it, page title, etc.)
    • Authenticate:
      Used to check if a username and password are valid. Access restricted, more information available later at the end of this article.

    As you see, the API of bit.ly is the most sophisticated yet powerful API compared to the APIs of the other URL shortening services.

    • Input Arguments:

    Any URL passed to a function must be encoded first to eliminate the ‘#’, ‘?’, ‘=’ and other problematic characters in the URL. For encoding a URL, the function System.Net.Uri.EscapeUriString() is very sufficient.

    There’re three main required arguments that are used by all functions:

    • login:
      Username.
    • apiKey:
      The key used to authenticate the user access to the API.
    • format:
      The format (type) of returned data from functions.

    Those three are required by all functions and you cannot work without one of them.

    • Authentication:

    All functions require user authentication. The user can prove his identity using his login name (username) and his API key (not his password.) You can get your API key by accessing the page http://bit.ly/a/account (after logging on to your account) or directly from http://bit.ly/a/your_api_key.

    One of the hot features of the API is that it provides you a demo user that can be used in your API training, the information of that user is as follows:

    Username: bitlyapidemo

    API Key: R_0da49e0a9118ff35f52f629d2d71bf07

    You might face problems with this account like violation of rate limits and many other problems, and that because it’s used by many users in the same time. Therefore, it’s recommended that you use another account.

    • Supported Formats:

    The API supports two formats of its returned data, XML and JSON (the default.) Yes it supports plain text too, but it’s not supported by all functions. XML data is easily manipulated by XML, so we’ll concentrate on XML besides the plain text format of course.

    • Handling Errors:

    If the function failed and you have specified the format as Plain Text (txt) in the call, you get an exception thrown in your code. If the format was XML, you can check the returned data for whether the function succeeded or not.

    The XML data returned from functions must follow this schema:

    <?xml version="1.0" encoding="UTF-8"?>
    <response>
        <status_code />
        <status_txt />
        ...
    </response>

    Here we have status_code set to the value 200 if the function succeeded and to the error code if the function failed. The status_txt describes the status of the function, it’s set to ‘OK’ if the function succeeded and to the error description if the function failed.

    The rest of the XML data is defined based on the function.

    • Preferred Domain:

    You have the option to use one of two domains, http://bit.ly and http://j.mp (new,) both offer you the same functionality and the same flexibility, however, the first counts to 20 characters while the other counts to only 18. (The domain can be set in the shortening function in the argument domain.)

    Keep in mind that the code just after the domain name (e.g. bnPuEX of http://bit.ly/bnPuEX) is called Hash and it is exactly 6 characters (case-sensitive.)

    There’re two types of hash, each short URL has many hashes:

    • User Hash:
      That hash of the URL generated for a given user shortened the URL. That means that a long URL might have more than one user hash equals to the number of users shortened that URL. (More than one hash means more than one short URL.)
    • Global Hash:
      A hash that is shared by all users for the same short URL.

    Thus, a short URL has only one global hash, but it might have more than one user hash (for each user shortened the same long URL.)

    • Rate Limits:

    You cannot think about making thousands of function calls every hour, access to the API is limited for each user on an hourly base. Limits are very sufficient for your application, but it’s going not to be sufficient if you are willing to spam the service or to drop it!

    Function Explanation

    Now we are going to talk about each function and how you can call it.

    First, get your API key that will be used to authenticate your calls to the API. If you need to bother yourself and to clog your application use the demo API user bitlyapidemo that have the API key R_0da49e0a9118ff35f52f629d2d71bf07.

    Shortening Function

    The first function we are going to talk about today is the shortening function, shorten. This function has the following address http://api.bit.ly/v3/shorten (as you expected) and is used to shorten long URLs. Besides main arguments key, apiKey, and format, it takes two more:

    • longUrl:
      The long URL to be shortened.
    • domain:
      Optional. The preferred domain, bit.ly or j.mp.

    You can get hands on this function and try it simply by navigating to the results of the following URL:

    http://api.bit.ly/v3/shorten?login=bitlyapidemo&apiKey=R_0da49e0a9118ff35f52f629d2d71bf07 &format=txt&longUrl=http://JustLikeAMagic.com

    This call simply tries to shorten the URL http://JustLikeAMagic.com by using credentials of the demo API user (substitute the current information with your own.) The format is set to plain text.

    You can also use change the format to XML and get output like this:

    <?xml version="1.0" encoding="utf-8"?>
    <response>
        <status_code>200</status_code>
        <status_txt>OK</status_txt>
        <data>
            <url>http://bit.ly/bO9TgE</url>
            <hash>bO9TgE</hash>
            <global_hash>9gSDEU</global_hash>
            <long_url>http://JustLikeAMagic.com&lt/long_url>
            <new_hash>0</new_hash>
        </data>
    </response>

    Notice that the status code is 200 that means that everything went ‘OK’. Notice that we have 5 elements:

    • url:
      The long URL generated.
    • hash:
      The user hash string.
    • global_hash:
      The globally shared hash. Can be used to browse to the URL too, it would be counted in the global statistics but not in user’s.
    • long_url:
      The original URL.
    • new_hash:
      Equals to 1 if this is the first time that URL being shortened (using the bit.ly service of course,) or 0 otherwise.

    Now, let’s code! The following function accepts a long URL and user API credentials and tries to shorten the URL using our shortening function.

    Don’t forget to add using statements to namespaces System.IO, System.Net, and System.Xml to that code and to the other code demonstrated in this article.

    // C#
    
    string Shorten(string url, string login, string key, bool xml)
    {
        url = Uri.EscapeUriString(url);
        string reqUri =
            String.Format("http://api.bit.ly/v3/shorten?" +
            "login={0}&apiKey={1}&format={2}&longUrl={3}",
            login, key, xml ? "xml" : "txt", url);
    
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(reqUri);
        req.Timeout = 10000; // 10 seconds
    
        // if the function fails and format==txt throws an exception
        Stream stm = req.GetResponse().GetResponseStream();
    
        if (xml)
        {
            XmlDocument doc = new XmlDocument();
            doc.Load(stm);
    
            // error checking for xml
            if (doc["response"]["status_code"].InnerText != "200")
                throw new WebException(doc["response"]["status_txt"].InnerText);
    
            return doc["response"]["data"]["url"].InnerText;
        }
        else // Text
            using (StreamReader reader = new StreamReader(stm))
                return reader.ReadLine();
    }

    Take notice of the mechanism used to check for errors.

    Expanding Function

    The next function we have is the function that is used to expand a URL, i.e., to get the long URL from the short one. Obviously, this function is called expand and it accepts the short URL shortUrl besides the three main arguments.

    Likewise, calling this function generate a data based on the function format, txt, xml, or json. The following XML data is generated when the function is called while the format is set to xml:

    <?xml version="1.0" encoding="utf-8" ?>
    <response>
        <status_code>200</status_code>
        <status_txt>OK</status_txt>
        <data>
            <entry>
                <short_url>http://bit.ly/bnPuEX</short_url>
                <long_url>http://justlikeamagic.com</long_url>
                <user_hash>bnPuEX</user_hash>
                <global_hash>bdE96m</global_hash>
            </entry>
        </data>
    </response>

    Now you can see the two hashes, user_hash and global_hash, and the two lend the user to your page (although the access is counted differently.)

    Now, let’s code! The following function retrieves the long URL from the short one:

    // C#
    
    string Expand(string url, string login, string key, bool xml)
    {
        url = Uri.EscapeUriString(url);
        string reqUri =
            String.Format("http://api.bit.ly/v3/expand?" +
            "login={0}&apiKey={1}&format={2}&shortUrl={3}",
            login, key, xml ? "xml" : "txt", url);
    
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(reqUri);
        req.Timeout = 10000; // 10 seconds
    
        // if the function fails and format==txt throws an exception
        Stream stm = req.GetResponse().GetResponseStream();
    
        if (xml)
        {
            XmlDocument doc = new XmlDocument();
            doc.Load(stm);
    
            // error checking for xml
            if (doc["response"]["status_code"].InnerText != "200")
                throw new WebException(doc["response"]["status_txt"].InnerText);
    
            return doc["response"]["data"]["entry"]["long_url"].InnerText;
        }
        else // Text
            using (StreamReader reader = new StreamReader(stm))
                return reader.ReadLine();
    }

    Validation Function

    The function validate is used to check if another username and API key pair is valid. For this function to work, you should use valid API credentials to check for the other credentials if they are valid or not. Therefore, you are going to use two additional arguments for the additional credentials, x_login and x_apiKey.

    This function doesn’t support plain text format. If XML was used, the function returns data like the following:

    <?xml version="1.0" encoding="UTF-8"?>
    <response>
        <status_code>200</status_code>
        <status_txt>OK</status_txt>
        <data>
            <valid>0</valid>
        </data>
    </response>

    The valid element is set to 1 if the credentials were OK or 0 otherwise.

    And this is our C# function that validates user API credentials:

    // C#
    
    string Validate(string login, string key,
        string xLogin, string xKey, bool xml)
    {
        string reqUri =
            String.Format("http://api.bit.ly/v3/validate?" +
            "login={0}&apiKey={1}&x_login={4}&x_key={5}&format={2}" +
            login, key, xLogin, xKey, xml ? "xml" : "txt");
    
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(reqUri);
        req.Timeout = 10000; // 10 seconds
    
        // if the function fails and format==txt throws an exception
        Stream stm = req.GetResponse().GetResponseStream();
    
        if (xml)
        {
            XmlDocument doc = new XmlDocument();
            doc.Load(stm);
    
            // error checking for xml
            if (doc["response"]["status_code"].InnerText != "200")
                throw new WebException(doc["response"]["status_txt"].InnerText);
    
            return int.Parse(doc["response"]["data"]["valid"]) == 1 ? true : false;
        }
        else // Text
            using (StreamReader reader = new StreamReader(stm))
                return int.Parse(reader.ReadLine()) == 1 ? true : false;
    }

    Stats Function

    This function is used to get stats about the short URL; the stats are represented in two values, user clicks and global clicks. User clicks value is the number of access times made to that user link. Global clicks value is the number of access times made from all short URLs (from all users) refer to the same address (almost like user hashes and global hash.)

    The function only accepts the short URL, shortUrl, besides the three main arguments. The data returned from the function is almost like this (in XML):

    <?xml version="1.0" encoding="utf-8" ?>
    <response>
        <status_code>200</status_code>
        <data>
            <clicks>
                <short_url>http://bit.ly/bnPuEX</short_url>
                <global_hash>bdE96m</global_hash>
                <user_clicks>0</user_clicks>
                <user_hash>bnPuEX</user_hash>
                <global_clicks>0</global_clicks>
            </clicks>
        </data>
        <status_txt>OK</status_txt>
    </response>

    The following C# function is used to retrieve number of access times for the current user and for all users:

    // C#
    
    int GetClicks(string url, string login, string key, out int globalClicks)
    {
        url = Uri.EscapeUriString(url);
        string reqUri =
            String.Format("http://api.bit.ly/v3/clicks?" +
            "login={0}&apiKey={1}&shortUrl={2}&format=xml" +
            login, key, url);
    
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(reqUri);
        req.Timeout = 10000; // 10 seconds
    
        Stream stm = req.GetResponse().GetResponseStream();
    
        XmlDocument doc = new XmlDocument();
        doc.Load(stm);
    
        // error checking for xml
        if (doc["response"]["status_code"].InnerText != "200")
            throw new WebException(doc["response"]["status_txt"].InnerText);
    
        XmlElement el = doc["response"]["data"]["clicks"];
        globalClicks = int.Parse(el["global_clicks"].InnerText);
        return int.Parse(el["user_clicks"].InnerText);
    }

    Lookup Function

    This function is used with long URLs to check whether they have been shortened before, and if so, the function returns the short URLs.

    If the long URL was found in service database, XML data like this is returned:

    <?xml version="1.0" encoding="utf-8" ?>
    <response>
        <status_code>200</status_code>
        <status_txt>OK</status_txt>
        <data>
            <lookup>
                <url>http://JustLikeAMagic.com</url>
                <short_url>http://bit.ly/9gSDEU</short_url>
                <global_hash>9gSDEU</global_hash>
            </lookup>
        </data>
    </response>

    Otherwise, you get another form of XML data:

    <?xml version="1.0" encoding="utf-8" ?>
    <response>
        <status_code>200</status_code>
        <status_txt>OK</status_txt>
        <data>
            <lookup>
                <url>http://JustLikeAMagic.com/books</url>
                <error>NOT_FOUND</error>
            </lookup>
        </data>
    </response>

    The following C# function looks-up a URL and returns its short URL if found:

    // C#
    
    string Lookup(string url, string login, string key)
    {
        url = Uri.EscapeUriString(url);
        string reqUri =
            String.Format("http://api.bit.ly/v3/lookup?" +
            "login={0}&apiKey={1}&url={2}&format=xml" +
            login, key, url);
    
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(reqUri);
        req.Timeout = 10000; // 10 seconds
    
        Stream stm = req.GetResponse().GetResponseStream();
    
        XmlDocument doc = new XmlDocument();
        doc.Load(stm);
    
        // error checking for xml
        if (doc["response"]["status_code"].InnerText != "200")
            throw new WebException(doc["response"]["status_txt"].InnerText);
    
        if (doc["response"]["data"]["lookup"]["error"] == null)
            return null; // not found
    
        return doc["response"]["data"]["lookup"]["short_url"].InnerText;
    }

    Info Function

    The info function is used to retrieve information about the current short URL. This function returns XML data like the following:

    <?xml version="1.0" encoding="utf-8" ?>
    <response>
        <status_code>200</status_code>
        <status_txt>OK</status_txt>
        <data>
            <info>
                <short_url>http://bit.ly/bnPuEX</short_url>
                <global_hash>bdE96m</global_hash>
                <user_hash>bnPuEX</user_hash>
                <created_by>elsheimy</created_by>
                <title>Just Like a Magic</title>
            </info>
        </data>
    </response>

    Besides link hashes, it returns the name of user who created it and the page title.

    And this is our C# function that retrieves that information:

    // C# Code
    
    string GetInfo(string url, string login, string key, out string createdBy)
    {
        url = Uri.EscapeUriString(url);
        string reqUri =
            String.Format("http://api.bit.ly/v3/info?" +
            "login={0}&apiKey={1}&shortUrl={2}&format=xml" +
            login, key, url);
    
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(reqUri);
        req.Timeout = 10000; // 10 seconds
    
        Stream stm = req.GetResponse().GetResponseStream();
    
        XmlDocument doc = new XmlDocument();
        doc.Load(stm);
    
        // error checking for xml
        if (doc["response"]["status_code"].InnerText != "200")
            throw new WebException(doc["response"]["status_txt"].InnerText);
    
        XmlElement el = doc["response"]["data"]["info"];
        createdBy = el["created_by"].InnerText;
        return el["title"].InnerText;
    }

    Authentication Function

    This is the last function today, the authenticate function. This function is used to check whether a username and a password are valid. Although this function and the validation function work the same way, there’s a big difference. The validation function checks for API credentials, the username and the API key, while this function checks for login information, the username and the password. Another big difference is that this function is currently access-restricted and you cannot use it before asking for permission from api@bit.ly.

    This function accepts two addition parameters, the username x_login and the password x_password.

    This function is called in a very specific way. You add arguments in the body of your request. In addition, the request is made by the method POST.

    If the function succeeded you get the API key for that user. For example:

    <?xml version="1.0" encoding="UTF-8"?>
    <response>
        <status_code>200</status_code>
        <data>
            <authenticate>
                <username>bitlyapidemo</username>
                <successful>1</successful>
                <api_key>R_0da49e0a9118ff35f52f629d2d71bf07</api_key>
            </authenticate>
        </data>
        <status_txt>OK</status_txt>
    </response>

    Otherwise, the successful element is set to 0 and no other information is available:

    <?xml version="1.0" encoding="UTF-8"?>
    <response>
        <status_code>200</status_code>
        <data>
            <authenticate>
                <successful>0</successful>
            </authenticate>
        </data>
        <status_txt>OK</status_txt>
    </response>

    The next C# function tries to authenticate a given user and retrieve his API key (Notice how to set information in the body of the request):

    // C#
    
    string Authenticate(string login, string key, string xLogin, string xPassword)
    {
        string reqUri = "http://api.bit.ly/v3/authenticate";
        string body =
            string.Format("login={0}&apiKey={1}&x_login={2}" +
            "&x_password={3}&format=xml",
            login, key, xLogin,xPassword);
    
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(reqUri);
        req.Timeout = 10000;
        req.Method = "POST";
    
        StreamWriter writer = new StreamWriter(req.GetRequestStream());
        writer.WriteLine(body);
    
        Stream stm = req.GetResponse().GetResponseStream();
        XmlDocument doc = new XmlDocument();
        doc.Load(stm);
    
        // error checking for xml
        if (doc["response"]["status_code"].InnerText != "200")
            throw new WebException(doc["response"]["status_txt"].InnerText);
    
        XmlElement el = doc["response"]["data"]["authenticate"];
        if (el["successful"].InnerText == "1")
            return el["api_key"].InnerText;
        else
            return null;
    }

    JSON Support

    We have been talking about the API and its support for XML and plain text formats and we missed the third one (is also the default,) that is JSON (JavaScript Object Notation.) Although XML and plain-text are enough and sufficient for most applications, and they’re very easy too, there’re some times when you are forced to work with JSON (some web services support only JSON data.) At least for completeness’ sake, we need to know how to handle JSON data when we have it in our hands.

    Worth mentioning that JSON is not supported by versions before .NET 3.5.

    First thing to know about bit.ly API is that you can get JSON data out of a function by passing the value json to the format parameter. Other way is to omit the format parameter completely, that’s because JSON is the default format that will be used when the format parameter not specified.

    Let’s take the shortening function as an example. Try calling the shortening function specifying json in the format parameter or removing the parameter completely:

    http://api.bit.ly/v3/shorten?login=bitlyapidemo&apiKey=R_0da49e0a9118ff35f52f629d2d71bf07
    &format=json&longUrl=http://JustLikeAMagic.com

    When you call the previous function you get some results similar to those:

    {
        "status_code": 200, 
        "status_txt": "OK", 
        "data":
        {
            "long_url": "http://justlikeamagic.com",
            "url": "http://bit.ly/bnPuEX",
            "hash": "bnPuEX",
            "global_hash": "bdE96m",
            "new_hash": 0
        }
    }

    Can you notice the similarities between the structure of this JSON-formatted data and the XML-formatted data we have seen earlier? Actually, the structure is the same, there’s no difference except how data is formatted.

    Looking at this JSON snippet we can see that it’s just a structure contains a few members, every member has a name and value both separated by a colon (:) and each surrounded by double quotes, members are separated by commas (,), and the whole structure is surrounded by curly brackets. Worth mentioning that the data member is a compound data member, means that it defines some other members inside it.

    The first step in handling JSON data is to create .NET classes/structures from the JSON code keeping the same structure definitions and parameter names. For our example, we need to create the following classes:

    C#
    
        class ShortUrl
        {
            public int status_code;
            public string status_txt;
            public ShortUrlData data;
        }
    
        class ShortUrlData
        {
            public string long_url;
            public string url;
            public string hash;
            public string global_hash;
            public int new_hash;
        }

    Here comes the trick, the DataContractJsonSerializer class that’s available in the namespace System.Runtime.Serialization.Json which is available in System.Runtime.Serialization.dll for .NET 4.0 and in System.ServiceModel.Web.dll for .NET 3.5 (not available before version 3.5.)

    This class can be used in two ways: to serialize (i.e. generate JSON data from a structure) or to deserialize (i.e. return the data structure from JSON data) this data. To serialize some data you call any of the WriteXXX() functions (based on the data type,) to deserialize this data you call any of the ReadXXX() functions (based on the data type too.)

    After you add the right assembly to project references and import the namespace System.Runtime.Serialization.Json, you can now start coding:

    // C#
    
    ShortUrl Shorten(string url, string login, string key)
    {
        url = Uri.EscapeUriString(url);
        string reqUri =
            String.Format("http://api.bit.ly/v3/shorten?" +
            "login={0}&apiKey={1}&format={2}&longUrl={3}",
            login, key, "json", url);
    
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(reqUri);
        req.Timeout = 10000; // 10 seconds
    
        // if the function fails and format==txt throws an exception
        Stream stm = req.GetResponse().GetResponseStream();
    
        DataContractJsonSerializer con = 
            new DataContractJsonSerializer(typeof(ShortUrl));
        ShortUrl shortUrl = (ShortUrl)con.ReadObject(stm);
    
        return shortUrl;
    }

    Have fun with JSON!

    Sample

    Download the sample code here.

    Where to go next

    Read more about URL shortening services here.

    Consuming URL Shortening Services – Cligs

    هذه المقالة متوفرة أيضا باللغة العربية، اقرأها هنا.

    Read more about URL shortening services here.

    Source- Elsheimy.Samples.ShortenSvcs.zip

    Contents

    Contents of this article:

    • Contents
    • Overview
    • Introduction
    • Description
    • API
      • Shortening URLs
      • Expanding URLs
    • Where to go next

    Overview

    This is another article that talks about URL shortening services. Today we are going to talk about Cligs, one of the popular shortening services on the web.

    Be prepared!

    Introduction

    Today we are talking about another popular shortening service; it’s Cligs, one of the most popular shortening services that provide lots of premium features for FREE.

    Enough talking, let’s begin the discussion.

    In December 2009, Cligs acquired by Mister Wong (a very nice bookmarking service.)

    Description

    How Cligs can help you? Cligs gives you plenty of features, including the following:

    • Shortening URLs (registered and non-registered users):
      You get a short URL that’s no more than 20 characters (Tweetburner is 22 and is.gd is only 18) including the domain http://cli.gs.
    • URL Management (registered users only):
      It allows you to manage your short URLs, to edit them, and to remove them if you like.
    • Real-time Analytics (registered users only):
      How many clicked your link, and when.
    • URL Previewing (registered and non-registered users):
      Preview the URL before opening it. Protects you from spam and unwanted sites.

    API

    Cligs provides you a very nice API with many advantages. The first advantage that we want to talk about is its simplicity. The API is very simple; it has just two functions, one for shortening URLs, and the other for expanding short URLs (to expand a URL means to get the long URL from the short one.)

    Another advantage of this API is that it allows you to shorten the URLs whether you are a registered user or not. Of course a registered user need to get an API key in order to link the API calls to his accounts so he can manage the links generated by the API and to watch the analytics.

    Shortening URLs

    The first function is used for shortening URLs and it’s called, create. This function has the following address:

    http://cli.gs/api/v1/cligs/create?url={1}&title={2}&key={3}&appid={4}

    The API is still in version 1, that’s why you see ‘v1’ in the address. This function takes four parameters, only the first one is required, other parameters are used for authentication:

    1. url:
      Required. The URL to be shortened.
    2. title:
      Optional. For authenticated calls only. The name that would be displayed on the short URL in your control panel (used for managing your URLs.)
    3. key:
      Optional. If you are a registered user and you want to link the API calls to your account, you’ll need to enter your API key here.
    4. appid:
      Optional. If you have used an API key, then you have to provide your application name that used to generate this API call (help users know the source of the link.)

    So how can you use this function? If this is an anonymous call (i.e. no authentication details provided,) just call the function providing the long URL in its single required argument.

    If you need to link this call to a specific account, then you’ll need an API key, which the user can get by signing in to his Cligs account, choosing ‘My API Keys’, then clicking ‘Create New API Key’ (if he doesn’t have one you.) The last step generates an API key that’s no exactly 32 characters (see figure 1.)

    Figure 1 - Creating API Keys, Cligs

    After you get the API key, you can push it to the function along with your application name in the appid argument.

    What about the title argument? For registered users, they can access their clig list (see figure 2) and see the URLs they shortened and the titles they choose above each of the URLs.

    Figure 2 - My Cligs, Cligs

    Now, let’s code! The following function makes use of the Cligs API to shorten URLs. It accepts three arguments, the long URL, the API key, and the application name. If the API key is null (Nothing in VB.NET,) the call is made anonymously, otherwise, the API key and the application name are used.

    // C#
    
    string Shorten(string url, string key, string app)
    {
        url = Uri.EscapeUriString(url);
        string reqUri =
            String.Format(@"http://cli.gs/api/v1/cligs/create?url={0}", url);
        if (key != null)
            reqUri += "&key=" + key + "&appid=" + app;
    
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(reqUri);
        req.Timeout = 5000;
    
        try
        {
            using (System.IO.StreamReader reader =
                new System.IO.StreamReader(req.GetResponse().GetResponseStream()))
            {
                return reader.ReadLine();
            }
        }
        catch (WebException ex)
        {
            return ex.Message;
        }
    }
    ' VB.NET
    
    Function Shorten(ByVal url As String, _
                     ByVal key As String, ByVal app As String) As String
    
        url = Uri.EscapeUriString(url)
        Dim reqUri As String = _
            String.Format("http://cli.gs/api/v1/cligs/create?url={0}", url)
        If key Is Nothing Then
            reqUri &= "&key=" & key & "&appid=" & app
        End If
    
        Dim req As WebRequest = WebRequest.Create(reqUri)
        req.Timeout = 5000
    
        Try
            Dim reader As System.IO.StreamReader = _
                New System.IO.StreamReader(req.GetResponse().GetResponseStream())
    
            Dim retValue As String = reader.ReadLine()
            reader.Close()
    
            Return retValue
        Catch ex As WebException
            Return ex.Message
        End Try
    
    End Function

    Expanding URLs

    The other function we have today is the expand function that’s used to get the long URL from the short one (e.g. to expand the short URL http://cli.gs/p1hUnW to be http://JustLikeAMagic.com.) This function is very simple and it has the following address:

    http://cli.gs/api/v1/cligs/expand?clig={1}

    This function accepts only a single argument, that’s the clig (short URL) to be expanded. The clig can be specified using one of three ways:

    • The clig ID. e.g. p1hUnW.
    • The raw URL. e.g. http://cli.gs/p1hUnW.
    • The encoded URL. e.g. http%3A%2F%2Fcli.gs%2Fp1hUnW.

    You can read more about URL encoding here.

    Now it’s the time for code! The following function takes a clig and returns its original URL:

    // C#
    
    string Expand(string url)
    {
        url = Uri.EscapeUriString(url);
        string reqUri = String.Format(@"http://cli.gs/api/v1/cligs/expand?clig={0}", url);
    
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(reqUri);
        req.Timeout = 5000;
    
        try
        {
            using (System.IO.StreamReader reader =
                new System.IO.StreamReader(req.GetResponse().GetResponseStream()))
            {
                return reader.ReadLine();
            }
        }
        catch (WebException ex)
        {
            return ex.Message;
        }
    }
    ' VB.NET
    
    Function Expand(ByVal url As String) As String
    
        url = Uri.EscapeUriString(url)
        Dim reqUri As String = _
            String.Format("http://cli.gs/api/v1/cligs/expand?clig={0}", url)
    
        Dim req As WebRequest = WebRequest.Create(reqUri)
        req.Timeout = 5000
    
        Try
            Dim reader As System.IO.StreamReader = _
                New System.IO.StreamReader(req.GetResponse().GetResponseStream())
    
            Dim retValue As String = reader.ReadLine()
            reader.Close()
    
            Return retValue
        Catch ex As WebException
            Return ex.Message
        End Try
    
    End Function

    Where to go next

    Some other articles about URL shortening services are available here.

    Consuming URL Shortening Services – Tweetburner (twurl)

    هذه المقالة متوفرة أيضا باللغة العربية، اقرأها هنا.

    Read more about URL shortening services here.

    Source- Elsheimy.Samples.ShortenSvcs.zip

    Contents

    Contents of this article:

    • Contents
    • Overview
    • Introduction
    • Description
    • API
    • Where to go next

    Overview

    Just another article of the URL shortening services series.

    Today, we are going to talk about another hot and easy-to-use service, it’s Tweetburner. If you haven’t used it before, then it’s the time to.

    We’re going to discuss how to use Tweetburner first. After that, we’ll inspect its API and learn how to use it in your .NET application.

    Introduction

    Again, one of the most popular URL shortening services ever.

    Today is dedicated for Tweetburner (known as twurl,) one of the hot, simple, and easy-to-use shortening services that you can compare to is.gd.

    Description

    When you visit Tweetburner website (via http://tweetburner.com or http://twurl.nl,) you can see that it allows users to register to gain more functionalities (specifically, link analytics.) However, at the time of this writing, the account page is disabled for technical issues and nothing interesting would happen if you register there.

    One of the hot features of Tweetburner is that it allows you to post your links to twitter (you guessed) and friendfeed as soon as they’re shortened just click ‘Share this link’ before you leave the page.

    Figure 1 - Shortening a URL, Tweetburner

    Figure 2 - Sharing a URL, Tweetburner

    Unfortunately, you can’t benefit from this sharing feature programmatically, but of course, you can create your own routines.

    After shrinking your URL, you get a new short link about 22 characters long (18 in is.gd) prefixed with http://twurl.nl.

    API

    Actually, Tweetburner doesn’t help you with an API. Instead, it provides you with a simple web page (used for shortening URLs) that you can access it from your code and get your short URLs.

    Let’s try it! Browse to our key page, http://tweetburner.com/links, and push your long URL and click the shortening button.

    Figure 3 - Shortening Links API, Tweetburner

    So how you can access this page via your .NET application and fill in its single field? Let’s get the idea! If you check the API documentation page, you might find that you are required just to request information from that page, post it the required URL via a simple string included in the request body, link[url]={0} (where {0} is the long URL, and just wait for the response that would contain the short URL of course if the function succeed.

    Do you find that ‘link[url]={0}’ strange? Try this with me! Browse to our page, http://tweetburner.com/links, and save it as HTML in your PC (not required, just grab its HTML code.)

    Sure we are interested on this magical text box, so scroll down to its definition that looks like this:

    Notice that the text box is given the name ‘link[url]’, that’s why we push ‘link[url]={0}’ on the request body. Given that hot information, you can push any data to any web form, just get the information required.

    Now, let’s code! The next function browses to our page, http://tweetburner.com/links, pushes the long URL specified, and gets the short URL back from the server. (Remember to include the namespace System.Net for the code to work properly.)

    // C#
    
    string Short(string url)
    {
        url = Uri.EscapeUriString(url);
    
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://tweetburner.com/links");
        req.Timeout = 5000;
        req.Method = "POST";
        req.ContentType = "application/x-www-form-urlencoded";
    
        byte[] buffer = System.Text.Encoding.UTF8.GetBytes("link[url]=" + url);
        req.ContentLength = buffer.Length;
    
        System.IO.Stream ios = req.GetRequestStream();
        ios.Write(buffer, 0, buffer.Length);
    
        try
        {
    
            using (System.IO.StreamReader reader =
                new System.IO.StreamReader(req.GetResponse().GetResponseStream()))
            {
                return reader.ReadLine();
            }
        }
        catch (WebException ex)
        {
            return ex.Message;
        }
    }
    ' VB.NET
    
    Function Shorten(ByVal url As String) As String
        url = Uri.EscapeUriString(url)
    
        Dim req As HttpWebRequest = _
            CType(WebRequest.Create("http://tweetburner.com/links"), HttpWebRequest)
        req.Timeout = 5000
        req.Method = "POST"
        req.ContentType = "application/x-www-form-urlencoded"
    
        Dim buffer() As Byte = _
            System.Text.Encoding.UTF8.GetBytes("link[url]=" + url)
        req.ContentLength = buffer.Length
    
        Dim ios As System.IO.Stream = req.GetRequestStream()
        ios.Write(buffer, 0, buffer.Length)
    
        Try
            Dim reader As System.IO.StreamReader = _
                New System.IO.StreamReader(req.GetResponse().GetResponseStream())
    
            Dim retValue As String = reader.ReadLine()
    
            reader.Close()
    
            Return retValue
        Catch ex As WebException
            Return ex.Message
        End Try
    End Function

    Notice that we have specified the POST method because it’s required if you are going to change some data in the server. It’s worth mentioning too that we have set the content type to application/x-www-form-urlencoded because it’s required if you are going to push data to a web form (it’s usually perfect for all web forms except file-uploads.)

    In addition, we have included the input required in the request stream.

    What’s next

    Some other articles about URL shortening services are available here.

    Consuming URL Shortening Services – is.gd

    هذه المقالة متوفرة أيضا باللغة العربية، اقرأها هنا.

    Read more about URL Shortening Services here.

    Source- Elsheimy.Samples.ShortenSvcs.zip

    Contents

    Contents of this article:

    • Contents
    • Overview
    • Introduction
    • API
    • What’s next

    Overview

    Another article of our series that talks about accessing URL shortening services programmatically.

    This article is talking about is.gd shortening service, how you can use it, and how to access it via your C#/VB.NET application.

    Introduction

    is.gd is one of the most popular shortening services ever in the web because of its simple interface and its easy-to-use API.

    When you visit service website, http://is.gd, you can see that nothing easier from is.gd, just push your long URL into the text box and click the shortening button.

    API

    is.gd provides you a very simple easy-to-use API. This API contains only one function that’s used for shortening URLs. Another good thing is that this function doesn’t require any kind of authentication for users. Therefore, you need just to spam it with your long URL (as you did with the website.)

    This glorious function is called http://is.gd/api.php, it accepts only a single argument, longurl, which can be set to the long URL you need to shorten. When you call the function, it simply returns the shortened URL as plain text (no more overhead.)

    Now, let’s try this function. We’ll try to shorten the URL http://JustLikeAMagic.com with our function. First, connect the arguments, http://is.gd/api.php?longurl=http://JustLikeAMagic.com. Now copy this address and paste it into your favorite browser. If everything was OK, you should see the short URL after clicking €˜Go’ in the browser toolbar.

    Now, let’s do it in C# and VB.NET. Check the following function that tries to shorten long URLs via the id.gd API:

    // C#
    
    string Shorten(string url)
    {
        url = Uri.EscapeUriString(url);
        string reqUri = String.Format(@"http://is.gd/api.php?longurl={0}", url);
    
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(reqUri);
        req.Timeout = 5000;
    
        try
        {
            using (System.IO.StreamReader reader =
                new System.IO.StreamReader(req.GetResponse().GetResponseStream()))
            {
                return reader.ReadLine();
            }
        }
        catch (WebException ex)
        {
            return ex.Message;
        }
    }
    ' VB.NET
    
    Function Shorten(ByVal url As String) As String
    
        url = Uri.EscapeUriString(url)
        Dim reqUri As String = _
            String.Format("http://is.gd/api.php?longurl={0}", url)
        Dim req As WebRequest = WebRequest.Create(reqUri)
        req.Timeout = 5000
    
        Try
            Dim reader As System.IO.StreamReader = _
                New System.IO.StreamReader(req.GetResponse().GetResponseStream())
    
            Dim retValue As String = reader.ReadLine()
            reader.Dispose()
    
            Return retValue
        Catch ex As WebException
            Return ex.Message
        End Try
    
    End Function

    Notice that we have used the function System.Net.Uri.EscapeUriString() to eliminate unacceptable characters from the URL by encoding them.

    Notice too that we have included our code in a Try-Catch block so we can catch exceptions before they blow up our application.

    What’s next

    Consider reading other articles in this series here.

    Consuming URL Shortening Services – Introduction

    هذه المقالة متوفرة أيضا باللغة العربية، اقرأها هنا.

    Read more about URL shortening services here.

    Source- Elsheimy.Samples.ShortenSvcs.zip

    Contents

    Contents of this article:

    • Contents
    • Overview
    • Introduction
    • Accessing the API
    • Authentication
    • .NET Support
    • Encoding
    • Sample
    • Where to Go Next
    • Poll: What are your favorite URL shortening services?

    Overview

    This is the first article of our series that talks about accessing URL shortening services programmatically.

    Here we introduce new concepts like the REST API. We also have a brief discussion of URL shortening services APIs and how you can access them.

    In addition, we are going to talk about .NET support for the REST API and tools and techniques available that would help us during our journey through the API.

    A working example built using C# and WinForms is available at the end of this article.

    This article is the base for all other articles. Articles other than this discuss specific services and their APIs. We will make use of code and techniques discussed here throughout the rest of articles.

    Let’s go!

    Introduction

    URL shortening services are very popular these days since web addresses tend to be very long and very difficult to be exchanged via email or other micro-blogging services like Twitter.

    Today, there’re tenths of URL shortening services spread out all over the web. Most of them are listed in the following articles:

    In this series, we are going to talk about how to consume URL shortening services in your .NET application. In other words, we will discuss how to program URL shortening services; we mean how to access them programmatically. In addition, we will have a brief discussion of each service and its unique features.

    How we will go through this discussion? This is going to be a series of articles published regularly. Each article discusses a given shortening service from the following list (updated regularly, expect new services to be added):

    The preceding list may not be comprehensive, many other popular services exist. However, not all shortening services have APIs! The preceding list contains the shortening services we know that allow developers to consume their functionalities via an exposed API.

    Before we start with a specific service, let’s have a brief discussion of features of the API and how we can access them.

    Accessing the API

    Most APIs in the web are just REST (Representational State Transfer) web services. A REST web service is simply a collection of functions (HTTP endpoints) that can be used to retrieve data in a variety of formats (optional.)

    Given an endpoint (function) like http://ab.c/api/shrink, we could supply the required input arguments as query strings in the URL. For example, we could shorten the URL www.google.com using a call to the HTTP endpoint http://ab.c/api/shrink?url=www.google.com supplied with the required information. It is worth mentioning that every service has its own API functions and arguments. Although they all do the same thing (shortening the URL,) they differ in function and argument names.

    When you call a web function, you just end up with the results in the format used in that function (XML, Atom, JSON, etc.) The function could also return plain text! It’s all about the function documentation that you should check carefully before calling the function. In addition, the returned value from a function may also contain error details if the function didn’t success.

    Keep in mind that API calls are limited and you can’t just leave the shortening code in an end-less loop! Other limitations of specific APIs should be discussed later.

    Authentication

    Most URL shortening services allow users to consume the service without being registered, some of allow users to register, and others not. Many other services require users to be registered in order to use the service.

    Likewise, service APIs may or may not require user authentication. Some services give the user an API key that can be used in the authentication process. Other services require user to enter his login details in the API calls. Most use the API key approach.

    .NET Support

    Does .NET support the REST API? Sure! As long as REST web services are just collections of HTTP endpoints, we do not need to worry about accessing them from .NET since that the BCL offers us a bunch of classes (available in System.dll) that can help with HTTP requests and responses.

    In addition, we will rely heavily on classes of System.Xml.dll to handle the data returned from functions (we will make use of functions that support XML.)

    If we could write something in C# that calls our fake web function http://ab.c/api/shrink, we could end up with some code like this:

    // C#
    
    public void string Shorten(string url)
    {
        string reqUri = @"http://ab.c/api/shrink?url=" + url;
    
        WebRequest req = WebRequest.Create(reqUri);
        req.Timeout = 5000;
    
        XmlDocument doc = new XmlDocument();
        doc.Load(req.GetResponse().GetResponseStream());
    
        return HandleXml(doc);
    }
    ' VB.NET
    
    Function Shorten(ByVal url As String) As String
    
        Dim reqUri As String = "http://ab.c/api/shrink?url=" &amp; url
    
        Dim req As WebRequest = WebRequest.Create(reqUri)
        req.Timeout = 5000
    
        Dim doc As new XmlDocument()
        doc.Load(req.GetResponse().GetResponseStream())
    
        Return HandleXml(doc)
    
    End Function

    Encoding

    If the URL to shorten have special characters like ‘&’, ‘?’, ‘#’, or ‘ ‘, those characters should be handled first before the URL is sent to the shortening function.

    This special handling for URLs is usually called Percent-encoding or URL Encoding. This encoding replaces unsafe characters with their hexadecimal values preceded by percentage (‘%’) signs.

    There are many unsafe characters that should be percent-encoded including ‘$’, ‘+’, ‘&’, ‘:’, and ‘=’. A nice discussion of URL Encoding can be found in the article URL Encoding by Brian Wilson.

    Why unsafe characters are problematic? Consider the following example: we need to shorten the URL http://justlikeamagic.com/?s=twitter with our fake shortening service http://ab.c, we end up with a call to the function using the following address http://ab.c/api/shrink?url=http://justlikeamagic.com/?s=twitter. Now we have two ‘?’s!!!

    So how can we encode URLs? Simply use the EscapeUriString() function of System.Net.Uri class it would work well for us here. If you need a full-featured encoder; a procedure that would work for all and every situation, you will need to consider creating one yourself, or you can use this:

    // C#
    
    char[] _chars = new char[]
    {
         '%',
         '$' ,
         '&amp;',
         '+',
         ',',
         '/',
         ':',
         ';',
         '=',
         '?',
         '@',
         ' ',
         '"',
         '',
         '#',
         '{',
         '}',
         '|',
         '\',
         '^',
         '~',
         '[',
         ']',
         ''', };
    
    string EncodeUrl(string url)
    {
        for (int i = 0; i < _chars.GetUpperBound(0); i++)
            url = url.Replace(
                _chars[i].ToString(),
                string.Format("{0:X}", (int)_chars[i]));
    
        return url;
    }
    
    string DecodeUrl(string url)
    {
        for (int i = 0; i < _chars.GetUpperBound(0); i++)
            url = url.Replace(
                string.Format("{0:X}", (int)_chars[i]),
                _chars[i].ToString());
    
        return url;
    }

    ' VB.NET

    Private _chars() As String = _
    { _
    "%", _
    "$", _
    "&amp;", _
    "+", _
    ",", _
    "/", _
    ":", _
    ";", _
    "=", _
    "?", _
    "@", _
    " ", _
    "", _
    "”, _
    “#”, _
    “{“, _
    “}”, _
    “|”, _
    “”, _
    “^”, _
    “~”, _
    “[“, _
    “]”, _
    “‘”}

    Public Function EncodeUrl(ByVal url As String) As String
    For i As Integer = 0 To _chars.GetUpperBound(0) – 1
    url = url.Replace( _
    _chars(i).ToString(), _
    String.Format(“{0:X}”, CInt(_chars(i))))
    Next

    Return url
    End Function

    Public Function DecodeUrl(ByVal url As String) As String
    For i As Integer = 0 To _chars.GetUpperBound(0) – 1
    url = url.Replace( _
    String.Format(“{0:X}”, CInt(_chars(i))), _
    _chars(i))
    Next

    Return url
    End Function

    Sample

    Download the sample from here.

    Where to Go Next

    Now start with any shortening service you like (links are update regularly, new services will be available too):

    Or else, check our URL Shortening Services tag.

    Poll

    Setting Device Information in MCI

    هذه المقالة متوفرة أيضا باللغة العربية، اقرأها هنا.

    Interested in MCI multimedia processing? First check this article out if you didn’t:

    Creating a Sound Recorder in C and C#

    After we received your feedbacks and comments about th.e article, we decided to add a small appendix to the end of the article about setting information (volume, channel, sampling rate, etc.) to a MCI device (a Waveform device of course.)

    Like anything else in MCI, you can set device information using a MCI command (string/numeric), and this time it’s the MCI_SET command.

    This command is used to set information about a specific device. This command requires an input parameter of the MCI_SET_PARMS structure. However, that input parameter might have extended members for specific devices. Because we are concentrating of Waveform devices, so we are going to use the MCI_WAVE_SET_PARMS structure that contains the extended members for our device and is defined as following:

    typedef struct {
        DWORD_PTR dwCallback;
        DWORD     dwTimeFormat;
        DWORD     dwAudio;
        UINT      wInput;
        UINT      wOutput;
        WORD      wFormatTag;
        WORD      wReserved2;
        WORD      nChannels;
        WORD      wReserved3;
        DWORD     nSamplesPerSec;
        DWORD     nAvgBytesPerSec;
        WORD      nBlockAlign;
        WORD      wReserved4;
        WORD      wBitsPerSample;
        WORD      wReserved5;
    } MCI_WAVE_SET_PARMS;

    This structure contains all and every little piece of information that can be set to a device. I expect that you read the main article and you are already familiar with members like dwCallback (other members are self-explanatory) that we have talked about many times, and you are fine too with function calls and setting up input parameters, so I won’t get into the discussion of the structure or how you are going to use that command. However, if you need more help setting up the input parameters for the structure, you should take a brief look at the MCI_WAVE_SET_PARMS Structure documentation in the MSDN.

    As you know, the MCI_WAVE_SET_PARMS unmanaged structure can be marshaled in C# as following:

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
    public struct MCI_WAVE_SET_PARMS
    {
        public IntPtr dwCallback;
        public uint     dwTimeFormat;
        public uint     dwAudio;
        public uint      wInput;
        public uint      wOutput;
        public ushort      wFormatTag;
        public ushort      wReserved2;
        public ushort      nChannels;
        public ushort      wReserved3;
        public uint     nSamplesPerSec;
        public uint     nAvgBytesPerSec;
        public ushort      nBlockAlign;
        public ushort      wReserved4;
        public ushort      wBitsPerSample;
        public ushort      wReserved5;
    }

    Congratulations! You did set the device information! So how to get them back?

    This can be done through the MCI_STATUS (discussed earlier) by setting up the MCI_STATUS_ITEM flag and setting the query item to the required information you need to query about (like MCI_DGV_STATUS_VOLUME to query about volume.)

    More about the MCI_STATUS command can be found in the MSDN documentation.