سلام
من مدتی می خوام با سیلور لایت کار کنم ولی صفحه دیزاین اون لود نمی شه و بجای آن پیغام زیر نوشته. پروژه رو مجدد بیلد می کنم ولی فایده ای ندارد. 


System.NullReferenceException

Object reference not set to an instance of an object.

   at Microsoft.Windows.Design.Platform.SilverlightMetad  ataContext.SilverlightXamlExtensionImplementations  .<GetXmlNamespaceCompatibilityMappings>d__8.MoveNe  xt()

   at MS.Internal.Design.Metadata.ReflectionProjectNode.  BuildSubsumption()

   at MS.Internal.Design.Metadata.ReflectionProjectNode.  SubsumingNamespace(Identifier identifier)

   at MS.Internal.Design.Markup.XmlElement.BuildScope(Pr  efixScope parentScope, IParseContext context)

   at MS.Internal.Design.Markup.XmlElement.ConvertToXaml  (XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider)

   at MS.Internal.Design.DocumentModel.DocumentTrees.Mar  kup.XamlSourceDocument.FullParse(Boolean convertToXamlWithErrors)

   at MS.Internal.Design.DocumentModel.DocumentTrees.Mar  kup.XamlSourceDocument.get_RootItem()

   at Microsoft.Windows.Design.DocumentModel.Trees.Modif  iableDocumentTree.get_ModifiableRootItem()

   at Microsoft.Windows.Design.DocumentModel.MarkupDocum  entManagerBase.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.VSIsolated  View.Load()

   at MS.Internal.Designer.VSIsolatedDesigner.VSIsolated  DesignerFactory.Load(IsolatedView view)

   at MS.Internal.Host.Isolation.IsolatedDesigner.Bootst  rapProxy.LoadDesigner(IsolatedDesignerFactory factory, IsolatedView view)

   at MS.Internal.Host.Isolation.IsolatedDesigner.Bootst  rapProxy.LoadDesigner(IsolatedDesignerFactory factory, IsolatedView view)

   at MS.Internal.Host.Isolation.IsolatedDesigner.Load()

   at MS.Internal.Designer.DesignerPane.LoadDesignerView  ()