In this article I will discuss about RichTextBox in Windows Phone.

Let's write code:

Step 1: Create a Silverlight for Windows Phone project. 

Step 2: Add a RichTextBox and two buttons inside ContentPanel of MainPage.Xaml. In RichTextBox I haved used different formatting of text. Remember RichTextBox is readonly.

<RichTextBox x:Name="rtb" Margin="20,-300,0,0">
   <Paragraph FontSize="34">
   A
      <Italic>RichTextBox</Italic>
      <Bold>demo from</Bold> initial
      <Underline>XAML</Underline> .
   </Paragraph>
   <Paragraph>
      Visit the
         <Hyperlink NavigateUri="http://msdn.com" TargetName="_blank">MSDN</Hyperlink> site
   </Paragraph>
</RichTextBox>

<Button x:Name="GetRichTextBoxXAML" Margin="20,340,0,0" Height="80" Width="430" Click="GetRichTextBoxXAML_Click" Content="Get RichTextBox XAML" />
<Button x:Name="SetRichTextBoxXAML" Margin="20,480,0,0" Height="80" Width="430" Click="SetRichTextBoxXAML_Click" Content="Set RichTextBox XAML" />

Step 3: Add below OnNavigatedTo method in MainPage.Xaml.cs. In this method I placed code to see how to format code for RichTextBox in codebehind.

protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
   base.OnNavigatedTo(e);
   Run run = new Run();
   run.Text = "A";

   Italic italic = new Italic();
   italic.Inlines.Add(new Run() { Text = "RichTextBox" });

   Bold bold = new Bold();
   bold.Inlines.Add(new Run() { Text = "demo from" });

   Underline underline = new Underline();
   underline.Inlines.Add(new Run() { Text = "Codebehind" });

   Image img = new Image();
   img.Source = new BitmapImage(new Uri("Tile-Mix.png", UriKind.Relative));
   img.Height = 150;
   img.Width = 150;

   InlineUIContainer ui = new InlineUIContainer();
   ui.Child = img;

   Paragraph paragraph = new Paragraph();
   paragraph.Inlines.Add(run);
   paragraph.Inlines.Add(italic);
   paragraph.Inlines.Add(bold);
   paragraph.Inlines.Add(underline);
   paragraph.Inlines.Add(new LineBreak());
   paragraph.Inlines.Add(ui);
   rtb.Blocks.Add(paragraph);
}

Step 4: Add event handler of GetRichTextBoxXAML_Click. In the XAML you will notice there won't be any element of image which we have added in OnNavigatedTo method. The XAML property doesn't support InlineUIContainer.

private void GetRichTextBoxXAML_Click(object sender, RoutedEventArgs e)
{
   MessageBox.Show(rtb.Xaml);
}

Step 5: Add event handler to SetRichTextBoxXAML_Click. I put exact XAML of MainPage.Xaml to set in RichTextBox via codebehind.

private void SetRichTextBoxXAML_Click(object sender, RoutedEventArgs e)
{
   rtb.Xaml = "<Paragraph FontSize=\"34\">A<Italic>RichTextBox</Italic><Bold>demo from</Bold> initial<Underline>XAML</Underline> .</Paragraph><Paragraph>Visit the<Hyperlink NavigateUri=\"http://msdn.com\" TargetName=\"_blank\">MSDN</Hyperlink> site</Paragraph>";
}

Now when you press button Set RichTextBox XAML button you will get below exception.

Step 6: To fix the above exception we need to add Section element with NameSpace. Now the modified code of SetRichTextBoxXAML_Click would be.

private void SetRichTextBoxXAML_Click(object sender, RoutedEventArgs e)
{
   rtb.Xaml = "<Section xml:space=\"preserve\" HasTrailingParagraphBreakOnPaste=\"False\" xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\"><Paragraph FontSize=\"34\">A<Italic>RichTextBox</Italic><Bold>demo from</Bold> initial<Underline>XAML</Underline> .</Paragraph><Paragraph>Visit the<Hyperlink NavigateUri=\"http://msdn.com\" TargetName=\"_blank\">MSDN</Hyperlink> site</Paragraph></Section>";
}

This ends the article of RichTextBox in Windows Phone.