SilverLight 5 | Step Bi Step

System.NullReferenceException in Silverlight application designer in Visual Studio 2010

Posted by Rajanihanth in .Net, Silverlight on June 28, 2012

This is my Environment:

Windows 7 64 bit
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:

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)