Silverlight Designer Error

Silverlight Problem in Design Mode:

When Created Control in Silverlight I found error in design mode:

System.Reflection.TargetInvocationException [Async_ExceptionOccurred]Arguments: Debugging resource strings are unavailable. Often the key and arguments provide sufficient information to diagnose the problem. See http://go.microsoft.com/fwlink/?linkid=106663&Version=4.0.50401.0&File=System.dll&Key=Async_ExceptionOccurred

After many invesigation I discovered I used HtmlPage object (Need browser to execute this line of code).
To fix this didn't execute Html object in design mode example:

if (!DesignerProperties.IsInDesignTool) { var height = HtmlPage.Document.Body.GetProperty("clientHeight"); var width = HtmlPage.Document.Body.GetProperty("clientWidth"); this.LayoutRoot.Width = double.Parse(width.ToString()); this.LayoutRoot.Height = double.Parse(height.ToString()); }