Silverlight control not stretching to its full width when hosted in a SharePoint Web Part (continued)

When creating the sample I first tried

         <TextBlock x:Name="MarqueeTextBox" Foreground="White" FontFamily="Comic Sans MS"
                   FontSize="16" FontStyle="Italic" Width="Auto" Height="Auto" Padding="5"            
                   HorizontalAlignment="Stretch" VerticalAlignment="Stretch" TextWrapping="Wrap"                   
                   Text="This is a very long text that will be stretched automatically when the width of the containing web part changes."/>

but this didn’t make the text wrap through the canvas. This is because you need to specify a fixed width to make wrapping happen. If you want your text wrap through the canvas while stretching when the web part width changes, you have to add a little more code. First I changed the Width property to a fixed width:

         <TextBlock x:Name="MarqueeTextBox" Foreground="White" FontFamily="Comic Sans MS"
                   FontSize="16" FontStyle="Italic" Width="200" Height="Auto" Padding="5"            
                   HorizontalAlignment="Stretch" VerticalAlignment="Stretch" TextWrapping="Wrap"                   
                   Text="This is a very long text that will be stretched automatically when the width of the containing web part changes."/>

In code behind I defined a ResizeTextBlock method. This method resizes the width of the TextBlock and is executed when the Silverlight application loads. You also need to add an event handler for the SizeChanged event of the Silverlight control to ensure that the TextBlock is resized each time the web part width changes.

    public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();
            ResizeTextBlock();
            this.SizeChanged += new SizeChangedEventHandler(MainPage_SizeChanged);
        }
        void MainPage_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            ResizeTextBlock();
        }
    }

First i t ried to set the width of the TextBlock to the width of the root canvas:

As you can see, the LayoutRoot has no actual width because no Width property has been defined on the canvas. The same problem occurs when you want to set the width of the TextBlock to the width of the Silverlight control itself, using this.Width. You have to rely on the width that has been set on the web part. You can grab the actual width of the plug-in display area represented by App.Current.Host.Content. Be aware that the ActualWidth property and the ActualHeight property do not contain meaningful values until after the Content.Resized event occurs for the first time.

        private void ResizeTextBox()
        {
            if (App.Current.Host.Content.ActualWidth > 0)
            {
                MarqueeTextBox.Width = App.Current.Host.Content.ActualWidth;
            }
        }

The text now wraps over the width of the canvas: