title: WPF XAML Designer Crashes
body: <p>I have a Window, the only thing it has in it is a TextBlock. I'm getting ridiculous designer exceptions that is crashing the designer every time I change anything. I started removing everything trying to find the culprit of this error. And now I have nothing left, but the designer keeps throwing exceptions.</p>
  
  <pre><code>&lt;Window x:Class="Company.Product.Views.About"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      Height="397"
      Width="658"&gt;
  &lt;TextBlock&gt;Test&lt;/TextBlock&gt;
  &lt;/Window&gt;
  </code></pre>
  
  <p>code behind:</p>
  
  <pre><code>/// &lt;summary&gt;
      /// Interaction logic for Window1.xaml
      /// &lt;/summary&gt;
      public partial class About : Window
      {
          public About()
          {
              InitializeComponent();
          }
      }
  </code></pre>
  
  <p>If I "Click here to reload the designer" the window shows up, but then if I modify the text of TextBlock, I get an exception</p>
  
  <p><strong>Exception</strong></p>
  
  <pre><code>System.ArgumentNullException
  Value cannot be null.
     at System.RuntimeType.MakeGenericType(Type[] instantiation)
     at Microsoft.VisualStudio.Shell.Design.VsTargetFrameworkUtil.GetRuntimeType(Type type)
     at Microsoft.VisualStudio.Shell.Design.VsTargetFrameworkType.TryGetRuntimeType()
     at Microsoft.VisualStudio.Shell.Design.VsTargetFrameworkUtil.EnsureRuntimeType(Type type)
     at Microsoft.VisualStudio.Shell.Design.VsTargetFrameworkProvider.GetRuntimeType(Type reflectionType)
     at MS.Internal.Package.VSIsolationProviderService.RemoteReferenceProxy.VsReflectionResolver.GetRuntimeType(Type reflectionType)
     at Microsoft.Windows.Design.Metadata.ReflectionMetadataContext.CachingReflectionResolver.GetRuntimeType(Type reflectionType)
     at Microsoft.Windows.Design.Metadata.ReflectionMetadataContext.Microsoft.Windows.Design.Metadata.IReflectionResolver.GetRuntimeType(Type reflectionType)
     at MS.Internal.Metadata.ClrType.get_RuntimeMember()
     at MS.Internal.Metadata.ClrMember`1.Microsoft.Windows.Design.Metadata.Reflection.IReflectionMember.get_MemberInfo()
     at MS.Internal.Metadata.ClrType.Equals(Object obj)
     at System.Collections.Generic.ObjectEqualityComparer`1.Equals(T x, T y)
     at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
     at Microsoft.Windows.Design.Metadata.Xaml.XamlExtensionImplementations.&lt;&gt;c__DisplayClass5.&lt;FindAttachableProperties&gt;b__4(ITypeMetadata walkType)
     at MS.Internal.Design.Metadata.Xaml.XamlType.&lt;GetAllAttachableProperties&gt;d__7.MoveNext()
     at MS.Internal.Design.Metadata.Xaml.XamlType.&lt;FindAttachableProperties&gt;d__0.MoveNext()
     at Microsoft.Windows.Design.Metadata.Xaml.XamlExtensionImplementations.&lt;FindAttachableProperties&gt;d__7.MoveNext()
     at MS.Internal.VirtualModel.VirtualModelPropertyCollection.&lt;GetUncachedProperties&gt;d__0.MoveNext()
     at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
     at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
     at MS.Internal.VirtualModel.VirtualModelPropertyCollection.GetEnumerator()
     at MS.Internal.Designer.PropertyEditing.Model.Properties.ModelPropertyMerger.&lt;GetFirstProperties&gt;d__0.MoveNext()
     at MS.Internal.Designer.PropertyEditing.Views.PropertyEntryReader.RedraftEntries(IPropertyViewManager viewManager, Selection selection, Boolean attachedOnly, IEventCodeBehindProxy eventCodeBehindProxy, CategoryList categoryList)
     at MS.Internal.Designer.PropertyEditing.PropertyInspector.UpdateCategories(Selection selection, Boolean attachedOnly, IEntryReader entryReader)
     at MS.Internal.Designer.PropertyEditing.PropertyInspector.RefreshPropertyList(Boolean attachedOnly)
     at MS.Internal.Designer.PropertyEditing.PropertyInspector.OnSelectionChangedIdle()
     at MS.Internal.Designer.PropertyEditing.PropertyInspector.OnSelectionChangedIdleForced(Object sender, EventArgs e)
     at System.Windows.Threading.DispatcherTimer.FireTick(Object unused)
     at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
     at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
  </code></pre>
  
  <p>I'm left with no way to debug what the problem is, and frankly I getting frustrated considering there should be nothing on this simple example that should be crashing the designer. Any ideas?</p>
  
  <p><strong>Update</strong></p>
  
  <p>After re-installing and updating and reloading, problem went away temporarily. Now the problem is back again. </p>
  
  <p>Actually, I'm not sure if the problem ever went away. I've also tried VS safe mode, /resetsettings, and deleting my several cache folders in the VS folder.</p>
  
  <p><strong>Update2</strong></p>
  
  <p><a href="http://www.screencast.com/t/BNygIXHS" rel="nofollow">Here's a screencast which shows the problem</a> Excuse my resolution, I'm in portrait.</p>