System.NullReferenceException in Silverlight application designer in Visual Studio 2010

System.NullReferenceException in Silverlight application designer in Visual Studio 2010

This is my Environment:

1. Windows 7 64 bit
2. VisualStudio 2010 with SilverLight 4 developer runtime

Problem: After upgrading the SilverLight 5 client, I tried to create a SilverLight Application and then I have got the following wired error message on the design tab 

The text format of the error is:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

System.NullReferenceException Object reference not set to an instance of an object. at Microsoft.Windows.Design.Platform.SilverlightMetadataContext.SilverlightXamlExtensionImplementations.d__8.MoveNext() at MS.Internal.Design.Metadata.ReflectionProjectNode.BuildSubsumption() at MS.Internal.Design.Metadata.ReflectionProjectNode.SubsumingNamespace(Identifier identifier) at MS.Internal.Design.Markup.XmlElement.BuildScope(PrefixScope parentScope, IParseContext context) at MS.Internal.Design.Markup.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider) at MS.Internal.Design.DocumentModel.DocumentTrees.Markup.XamlSourceDocument.FullParse(Boolean convertToXamlWithErrors) at MS.Internal.Design.DocumentModel.DocumentTrees.Markup.XamlSourceDocument.get_RootItem() at Microsoft.Windows.Design.DocumentModel.Trees.ModifiableDocumentTree.get_ModifiableRootItem() at Microsoft.Windows.Design.DocumentModel.MarkupDocumentManagerBase.get_LoadState() at MS.Internal.Host.PersistenceSubsystem.Load() at MS.Internal.Host.Designer.Load() at MS.Internal.Designer.VSDesigner.Load() at MS.Internal.Designer.VSIsolatedDesigner.VSIsolatedView.Load() at MS.Internal.Designer.VSIsolatedDesigner.VSIsolatedDesignerFactory.Load(IsolatedView view) at MS.Internal.Host.Isolation.IsolatedDesigner.BootstrapProxy.LoadDesigner(IsolatedDesignerFactory factory, IsolatedView view) at MS.Internal.Host.Isolation.IsolatedDesigner.BootstrapProxy.LoadDesigner(IsolatedDesignerFactory factory, IsolatedView view) at MS.Internal.Host.Isolation.IsolatedDesigner.Load() at MS.Internal.Designer.DesignerPane.LoadDesignerView()

Solution: The problem is the conflict of SilverLight versions and I have found the solution in this thread.

Step 1: Uninstall the latest SilverLight client which is SilverLight  5, the 1st one in the below control panel screen shot

Step 2: Uninstall SilverLight 4 developer, the next 1 in the above image

Step 3: Download and Install Microsoft Silverlight 4 Tools for Visual Studio 2010 (Add-on and pre-requisite files for Visual Studio 2010 to develop Silverlight 4 and RIA Services applications)

Installing..!

Installation finished successfully.

Restart the VisualStudio 2010, wow.. it’s working! 

Happy Silverlighting..! Thanks R./