First you need to add a Reference > PresentationFramework.Aero from .NET Refrences Tab
Then Add this line of code into your resource dictionary on the top
xmlns:Microsoft_Windows_Themes="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Aero"
Then Add this line of code into your resource dictionary on the top
xmlns:Microsoft_Windows_Themes="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Aero"