Style.Seal Method
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Locks the style so that the TargetType property or any Setter in the Setters collection cannot be changed.
Assembly: System.Windows (in System.Windows.dll)
A Style is sealed either when the Seal method is called on the Style or when the Style is applied to a FrameworkElement. When a Style is sealed, all the base styles it derives from up the inheritance chain are also sealed.
If you try to change the TargetType or a Setter in the style after it has been sealed, an InvalidOperationException is thrown.