WPF C#

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Class="Microsoft.Samples.Graphics.RectangleExample"
    WindowTitle="Example">
  
              Name="MyFadingText"
        Margin="20" 
        Width="640" Height="100" FontSize="48" FontWeight="Bold" Foreground="Maroon">
        This is fading text
        
          
            
              
                                  Storyboard.TargetName="MyFadingText" 
                  Storyboard.TargetProperty="(TextBlock.Opacity)"
                  From="1.0" To="0.0" Duration="0:0:5" 
                  AutoReverse="True" RepeatBehavior="Forever" />