Introduction

In this article, we’ll have a brief discussion of the new features in elevated-trust applications in Silverlight 5.

Overview

Elevated-trust applications have undergone few changes in Silverlight 5:

• In-Browser Support
• Multiple Windows Support
• File System Access
• Platform Invocation

Let’s see those changes in details.

In-Browser Support

Unlike previous versions, in Silverlight 5 you don’t have to run your application as OOB to get elevated-trust features, you can now run elevated-trust applications in the browser and get all the features you need.

There’re two security considerations to be taken in order to run your elevated-trust application in browser:

1. You must enable running your application in browser via either the Client Access Policy file or the Windows Registry. Using the policy file allows your application to run in a private network. Using the Windows Registry approach allows your application to run on a single machine. In either approaches, you cannot deploy in-browser elevated-trust applications to everyone on the web.
2. In addition, your XAP must be signed with a trusted certificate e.g. X.509 certificate) available in the Trusted Publisher Certificate store.

Without any of those requirements, you won’t be able to run your elevated-trust application in browser. But wait, there’s a catch!

In your development machine you can run elevated-trust applications in browser only on whitelisted domains. For example, by default, localhost is whitelisted, so you can easily run an elevated-trust application in the browser in localhost. If you change to another domain, ensure that you add this name to the whitelist, or you won’t be able to run the application. More comes about this later.

The last thing to keep in mind is that in the Beta version, in-browser elevated-trust applications are supported in Windows only. Other platforms are going to be available in the final version.

Client Access Policy Approach

If you want your application to be available in a private network, you need to do some changes to the client access policy file in order to allow it to run in browser as elevated-trust. The changes are as the following; just set the ElevatedPermissions property of SecuritySettings to Required:

<Deployment.OutOfBrowserSettings>
  ...
  <OutOfBrowserSettings.SecuritySettings>
    <SecuritySettings ElevatedPermissions="Required" />
  <OutOfBrowserSettings.SecuritySettings>
  ...
</Deployment.OutOfBrowserSettings>

Windows Registry Approach

The other approach you have is to use the Windows Registry to enable in-browser elevated-trust applications to run on a particular machine. To do this, go to HKEY_LOCAL_MACHINESOFTWAREMicrosoftSilverlight. In this registry key, you have several values related to elevated-trust applications:

• AllowElevatedTrustAppsInBrowser:
  Set to TRUE (0x00000001) to enable running elevated-trust applications in browser.
• AllowInstallOfElevatedTrustApps:
  Set to TRUE to enable installation of elevated-trust applications to the PC (i.e. OOB.)
• AllowLaunchOfElevatedTrustApps:
  Set to TRUE to enable launching elevated-trust applications (in-browser or OOB.)

Example

To run an elevated-trust application in browser you need first to enable OOB and elevated-trust features from project properties. After that, create a Web application and link it to the Silverlight application to host it. If you didn’t do this, your Silverlight application will run as OOB. Your application is able now to run as elevated-trust in browser. To ensure this, you can check for the Application.HasElevatedPermissions property:

  theTextBlock.Text = "Is Elevated-Trust: " +
    Application.Current.HasElevatedPermissions.ToString();

Now try something more interesting. Try reading a file in the file system that only elevated-trust applications have access to:

theTextBlock.Text =
        File.ReadAllText(@"C:WindowsSystem32Driversetchosts");

As you see, the application works as expected, and has all the elevated-trust features as OOB applications.

Now let’s try changing the domain from localhost to another domain. Go to Web application project properties, switch to the Web tab, then go to Server settings and change the server from Visual Studio Development Server to Local IIS Web Server and use your machine name as the domain and save the settings. (You might be asked to confirm virtual directory creation, it’s because you have changed to another domain and used another virtual directory.)

Now try to run the application. The application won’t be able to run and you’ll get a security exception, that’s because the new domain is not whitelisted like localhost.

Multiple Windows Support

Multiple Windows Support or Ad-hoc Windows is a feature that enables elevated-trust OOB applications in Silverlight 5 to have windows other than the main window. The feature is available through the Window class which is now instantiable. You use the Window class to create another window and set its contents through the Content property and show it using the Visibility property.

The following code creates a Window that’s 400 pixels wide and 300 pixels long, and has just a button in the interface:

    Window wnd = new Window();
    wnd.Width = 400;
    wnd.Height = 300;
    wnd.Content = new Button { Content = "Say Hello" };
    wnd.Visibility = System.Windows.Visibility.Visible;

Notice that you can end the application by closing the main window; it doesn’t matter if you close any other window.

You’re not limited to just a button or a single object in the window contents. You can create another page (i.e. user control) and set it to be the content of the window:

    Window wnd = new Window();
    wnd.Width = 400;
    wnd.Height = 300;
    wnd.Content = new MyOtherPage();
    wnd.Visibility = System.Windows.Visibility.Visible;

And you can also create windows with custom chrome by removing the toolbar and borders and create them yourself via code:

    Window wnd = new Window();
    wnd.Width = 400;
    wnd.Height = 300;
    wnd.Content = new MyOtherPageWithCustomChrome();
    wnd.WindowStyle = WindowStyle.None;
    wnd.Visibility = System.Windows.Visibility.Visible;

Notice that if you don’t have elevated-trust features, you won’t be able to spawn other windows. And if you tried to, you’ll get a security exception.

File System Access

Unlike elevated-trust applications in Silverlight 4 which have access to only My Documents folder, Silverlight 5 elevated-trust applications (in-browser and out-of-browser) have full access to the file system. But keep in mind that although you have full access to the file system, you still restricted by the rights of the user running your application. If the user doesn’t have access to a specific file or folder, then you don’t have access to that file or folder.

To test this feature, try reading contents from a file in the system folder (for instance):

theTextBlock.Text =
        File.ReadAllText(@"C:WindowsSystem32Driversetchosts");

As you see, you have access to that file.

By default, if you’re running Windows Vista or Windows 7, your user wouldn’t have administrator privileges as long as he doesn’t launch Visual Studio (or your application) in elevated mode. So if you don’t have admin privileges and tries to gain the write access to the same file your application would fail, that’s because your application is restricted by user rights and the user don’t have write access to that file:

    File.AppendAllText
      (@"C:WindowsSystem32Driversetchosts",
      "nfoo");

Same results when trying to write to the system drive without elevated permissions for the user:

    File.WriteAllText(@"C:test.txt", "Foo");

Platform Invocation

Silverlight 4 has introduced support for automation and COM components. Silverlight 5 has added support for Platform Invocation (or P/Invoke.) Platform Invocation allows you to call native code (e.g. DLLs and Windows API) from your Silverlight application. This is a great improvement of course. It uses the same mechanism as other WinForms applications. Unfortunately, this feature is currently not available in the Beta.

Summary

The following changes have been happened to elevated-trust applications in Silverlight 5:

• In-Browser Support:
  You can now run elevated-trust applications in Silverlight 5 in browser. Must be enabled via client access policy file or Windows Registry, and XAP must be signed with a trusted certificate.
• Multiple Windows Support:
  Allows elevated-trust OOB applications to span windows other than the main window.
• File System Access:
  Allows you to have full access to the file system with the rights of the current user.
• Platform Invocation:
  Allows you to call native code like DLLs and Windows API from your Silverlight application. Not available in Beta.

Now, check out other What’s New in Silverlight 5? articles.

شاهد كورس كامل سيلفرلايت 5 مجانا هنا.

This content is based on Beta release, expect many changes in the final release.

Read What’s New in Silverlight 5 series here.

Download Sample Code

Introduction

In this article, we’ll have a brief discussion of the new features of controls and text in Silverlight 5.

Overview

Silverlight 5 has undergone few improvements in controls and text; new added features for controls, and rendering and performance enhancements for text.

The following are the new features of controls in Silverlight 5:

• Text tracking and leading control
• Text overflow
• Multi-click support
• Type-ahead text searching
• SaveFileDialog DefaultFilename
• DataContextChanged event (not in Beta)

And text has been improved in in a few ways:

• Rendering is now better
• Performance of text layout has been improved
• Text clarity is improved with Pixel Snapping
• OpenType support has been enhanced

As improvements in text were all about rendering and performance, we won’t talk more about the text improvements. Instead, we’ll focus in this article on control stack and cover the changes that happened to it in details.

Text Tracking and Leading Control

Silverlight 5 has added three features to text controls (TextBlock, TextBox, and RichTextBox) to allow you to control precisely text tracking and leading space for characters and lines:

• Character Spacing
• Line Height
• Line Stacking Strategy

Character Spacing

This feature allows you to precisely set how far apart each character is. This feature is available in all text controls through a property called CharacterSpacing that specifies the distance between characters. This distance is measured by 1000^th of the current font size, means that for instance if you set the font size to 20px and character spacing to 500, then the distance will be 10px between each character (since 20 * 500 / 1000 = 10px.)

Here’s an example of a TextBlock that uses the character spacing feature to put 10px between each character:

<TextBlock FontSize="20" CharacterSpacing="500">
  Lorem ipsum dolor sit amet, consectetur adipiscing elit.
</TextBlock>

Line Height

This feature allows you to set precisely the height of each line of the content in a text controls. It’s available in all text controls through a property called LineHeight and, unlike CharacterSpacing, it’s measured in pixels.

The following code sets the height of each line in the text to 50px:

<TextBlock Margin="5" LineHeight="50">
  Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  <LineBreak />
  Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  <LineBreak />
  Lorem ipsum dolor sit amet, consectetur adipiscing elit.
</TextBlock>

Line Stacking Strategy

This feature allows you to specify how each line box is determined. For example, if you’re in a scenario like the following where you have some text larger than other text, what will you do?  Would you increase the height for each line to accommodate the size for the larger text and allow the text to be readable?  Or would you leave the text as it as if there wasn’t any text with different font size? That’s what the stacking strategy is all about.

<TextBlock Margin="25" FontSize="12">
  Lorem ipsum <Span FontSize="20">dolor sit amet</Span>, ...
  <LineBreak />
  Proin aliquam augue quis ipsum <Span FontSize="38">rhoncus</Span> ...
  <LineBreak />
  Quisque eleifend ante vitae velit vehicula luctus. ...
</TextBlock>

The stacking strategy is available to your code through a new property called LineStackingStrategy. This property takes one value of three:

• MaxHeight (default):
  Increases the size of each line’s box enough to hold its content. If LineHeight is set, adds the value of LineHeight to the determined value of the height of line’s box.
• BlockLineHeight:
  Uses value from LineHeight if specified. Otherwise, increases the size for each line’s box to hold its various font sizes content.
• BaselineToBaseline:
  Uses value from LineHeight if sepified. Otherwise, uses the default line height that doesn’t care about whether the content has larger text or not.

The following figure compares between the three stacking strategies while setting LineHeight and while not setting it.

Makes sense?

Text Overflow

This feature allows for multi-column and free-form text layouts. It’s available for RichTextBoxes only. You set a RichTextBox as the master element, and link it to the new RichTextBoxOverflow to capture extra text that doesn’t fit in the master RichTextBox. You can also continue the chain and link another RichTextBoxOverflow to the previous one to capture extra text that doesn’t fit there and so on. To link an overflow control to another one, you use the new OverflowContentTarget property available in the previous control to bind to the next overflow control.

The following figure shows how you can use overflow controls to create multi-column text:

And the following shows an example of a free-form text where the text wraps around an object in the center:

The following example creates a multi-column text:

<Grid.ColumnDefinitions>
  <ColumnDefinition />
  <ColumnDefinition />
  <ColumnDefinition />
</Grid.ColumnDefinitions>

<RichTextBox OverflowContentTarget="{Binding ElementName=firstOverflow}" />

<RichTextBoxOverflow x:Name="firstOverflow" Grid.Column="1"
  OverflowContentTarget="{Binding ElementName=secondOverflow}"/>

<RichTextBoxOverflow x:Name="secondOverflow" Grid.Column="2" />

Multi-Click Support

Silverlight 5 now allows you to capture multi-clicks in controls. It can capture any n-clicks, but most of the time you’ll capture double-clicks and sometimes triple clicks. This feature is available through a property called ClickCount available in MouseButtonEventArgs. While MouseButtonEventArgs is available in ButtonDown and ButtonUp events, ClickCount is only valid on MouseLeftButtonDown and MouseRightButtonDown, it always return 1 from ButtonUp events.

The following code shows how you can capture multiple clicks in a TextBlock, it updates the TextBlock for each click:

private void theTextBlock_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
  if (e.ClickCount == 1)
    theTextBlock.Text += "Single-clickn";
  else if (e.ClickCount == 2)
    theTextBlock.Text += "Double-clicksn";
  else if (e.ClickCount == 3)
    theTextBlock.Text += "Triple-clicksn";
  else
    theTextBlock.Text += e.ClickCount.ToString() + "n";
}

Type-Ahead Text Searching

Type-ahead text searching capability in Silverlight 5 allows you to search in a collection control (e.g. ComboBox, ListBox, etc.) using keyboard; you reach the desired item by typing the first letters of its content.

The content that the control searches in must be specified in DisplayMemberPath. For example, in our books scenario to search in book titles you must set DisplayMemberPath to the Title field. This leads up to another problem, if you have set a data template, you cannot set DisplayMemberPath along with it. This problem can be solved by using the new Silverlight 5 XAML feature, implicit data templates, which has been covered earlier in the previous article.

In our books scenario, we have the following ComboBox that has an implicit data template applied:

<ComboBox x:Name="books" />

And we have also the following code that populates the ComboBox and sets the DisplayMemberPath to allow searching using keyboard:

books.ItemsSource = new BookData().OrderBy(b => b.Title);
books.DisplayMemberPath = "Title";

The application works perfectly now. But if you convert the data template to an explicit data template like the following:

<ComboBox x:Name="books>
  <ComboBox.ItemTemplate>
    <DataTemplate>
      <StackPanel>
        <TextBlock Text="{Binding Title}" FontWeight="Bold" />
        <TextBlock Text="{Binding Author}" />
        <TextBlock Text="{Binding Price, StringFormat='C'}" />
      </StackPanel>
    </DataTemplate>
  </ComboBox.ItemTemplate>
</ComboBox>

You receive the following error, because DisplayMemberPath cannot be set while setting an ItemTemplate:

SaveFileDialog DefaultFilename

Now in Silverlight 5 you can set the default filename in SaveFileDialog (using the new DefaultFileName property) that will show in the file name box when you launch the dialog:

SaveFileDialog dialog = new SaveFileDialog();
dialog.DefaultFileName = "Foo";
dialog.ShowDialog();

DataContextChanged Event

This feature is currently not available in Beta; it should be available in the final version. It occurs when the DataContext object for a control changes.

Summary

For controls in Silverlight 5, we have the following improvements:

• Text tracking and leading control:
  Allows you to set character spacing, line height, and line stacking strategy for a text control.
• Text overflow:
  Available for RichTextBoxes. Allows for multi-column and free-form text layouts.
• Multi-click support:
  Allows you to capture any n-clicks.
• Type-ahead text searching:
  Allows searching in a collection control using keyboard.
• SaveFileDialog DefaultFilename:
  Allows you to set the default file name for SaveFileDialog.
• DataContextChanged event:
  Not in beta. Occurs when the DataContext object for a control changes.

And in the text stack, there were some improvements related to performance and rendering:

• Rendering is now better
• Performance of text layout has been improved
• Text clarity is improved with Pixel Snapping
• OpenType support has been enhanced

Now, check out other What’s New in Silverlight 5? articles.