What factors determine whether the MS developers disallow inheritance from a control? (I'm assuming there are some common underlying reasons?)
Perusing the Windows.UI.Xaml.Controls namespace, I don't see any mention or obvious pattern as to why some controls are declared with the final/sealed specifier while others aren't. Certainly, someone, somewhere must have wanted to derive from, say, TextBlock, only to be disappointed. But why forbid this behavior? What makes a control like Image final but not MediaTransportControls?