Silverlight designer :An error as "An unhandled exception has occurred "

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if the XAML file is closed and you open it, the following message appears in Design view of the WPF Designer:

An unhandled exception has occurred.

Click here to reload the designer

Details: System.NullReferenceException
Object reference not set to an instance of an object.
   at Microsoft.Windows.Design.Platform.SilverlightMetadataContext.SilverlightXamlExtensionImplementations.<GetXmlNamespaceCompatibilityMappings>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()

Posted 17-Feb-13 21:06pm

naveen kapavarapu

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2 solutions

Solution 1

Hi. i guess you have a control that has some property like DataGrid.ItemsSource and you populate it in code behind. i suppose we are a DataGrid and its name is "MainDataGrid".your Xaml is like this(for example):

XML

<DataGrid x:Name="MainDataGrid" Loaded="MainDataGrid_Loaded">

       </DataGrid>

and in your codeBehind you must write:
using System.ComponentModel;

then:

XML

private void MainDataGrid_Loaded(object sender, RoutedEventArgs e)
        {
            if (!DesignerProperties.GetIsInDesignMode(this))
            {
                MainDataGrid.ItemsSource=//a method that return a list or a List<yourSpecifiedType>
            }
        }

maybe your ItemsSource is filled by null.

good luck

Posted 18-Feb-13 1:07am

aliwpf

Updated 18-Feb-13 1:09am

v2

Comments

naveen kapavarapu 18-Feb-13 7:40am

Sorry,Its not working sir ,thanku

aliwpf 18-Feb-13 10:29am

do you have a ItemsContorl like DataGrid or ListBox in your application?

naveen kapavarapu 19-Feb-13 5:04am

I am not installing visualStudio2010 Servivepack1,that way the problem is rise..Thank you sir

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naveen kapavarapu · Accepted Answer · 2013-02-18T23:01:00

Solution 2

Just,I am install Visual Studio 2010 Service pack1 then my design form(XAML)page is loaded..
The problem is i am not install the Visual Studio 2010 Service pack1 that's way error is rise..thanku

Posted 18-Feb-13 23:01pm

naveen kapavarapu

Updated 18-Feb-13 23:08pm

v2