Settings.EnableRedrawRegions Property

// The Host object, which represents the host Silverlight plug-in.
System.Windows.Interop.SilverlightHost host = 
    Application.Current.Host;

// The following code demonstrates how to use the Host object
// to access other APIs in the System.Windows.Interop namespace.

// The IsVersionSupported method. This method is useful when
// you want to implement an upgrade experience in managed code.
bool isSupported = host.IsVersionSupported("2.0.30908.0");

// Read-only properties of the Host object.
System.Windows.Media.Color pluginBackground = host.Background;
bool loaded = host.IsLoaded;
Uri source = host.Source;

// The Settings object, which represents Web browser settings.
System.Windows.Interop.Settings settings = host.Settings;

// Read/write properties of the Settings object.
settings.EnableFrameRateCounter = true;
settings.EnableRedrawRegions = true;
settings.MaxFrameRate = 60;

// Read-only properties of the Settings object.
bool windowless = settings.Windowless;
bool htmlAccessEnabled = settings.EnableHTMLAccess;

// The Content object, which represents the plug-in display area.
System.Windows.Interop.Content content = host.Content;

// The read/write IsFullScreen property of the Content object.
// See also the Content.FullScreenChanged event.
bool isFullScreen = content.IsFullScreen;

// Read-only properties of the Content object. These properties do 
// not contain meaningful values until after the Content.Resized 
// event occurs for the first time. 
double actualWidth = content.ActualWidth;
double actualHeight = content.ActualHeight;