title: NotImplementedException 0x80004001 after updating property in ViewModel
body: <p>The context is a Silverlight application for Windows Phone 7. I am debugging with the emulator.</p>
  
  <p>I have a <code>MainPage.xaml</code> with a ViewModel attached in its DataContext.<br>
  When the page is <code>NavigatedTo</code>, a method is called in the ViewModel to call an API and display information.</p>
  
  <p>I have a method which create a <code>Dictionary&lt;string, string&gt;</code>, fill it with data and set it in a property implementing the <code>PropertyChanged</code> event.</p>
  
  <p>After this method is called, the debugger breaks in App.Application_UnhandledException with a NotImplementedException.</p>
  
  <p>If I skip the call to this method with the debugger, the exception is not raised.</p>
  
  <p>The strange thing is that the exception is raised after calling the method and not within! The exception contains no InnerException. There is a HResult of -2147467263 and a message containing "0x80004001". Here is the StackTrace:</p>
  
  <pre><code>at MS.Internal.XcpImports.CheckHResult(UInt32 hr)
  at MS.Internal.XcpImports.FrameworkElement_MeasureOverride(FrameworkElement element, Size availableSize)
  at System.Windows.FrameworkElement.MeasureOverride(Size availableSize)
  at System.Windows.FrameworkElement.MeasureOverride(IntPtr nativeTarget, Single inWidth, Single inHeight, Single&amp; outWidth, Single&amp; outHeight)
  at MS.Internal.XcpImports.MeasureNative(IntPtr element, Single inWidth, Single inHeight)
  at MS.Internal.XcpImports.UIElement_Measure(UIElement element, Size availableSize)
  at System.Windows.UIElement.Measure(Size availableSize)
  at Microsoft.Phone.Controls.Primitives.PanoramaPanel.MeasureOverride(Size availableSize)
  at System.Windows.FrameworkElement.MeasureOverride(IntPtr nativeTarget, Single inWidth, Single inHeight, Single&amp; outWidth, Single&amp; outHeight)
  at MS.Internal.XcpImports.MeasureOverrideNative(IntPtr element, Single inWidth, Single inHeight, Single&amp; outWidth, Single&amp; outHeight)
  at MS.Internal.XcpImports.FrameworkElement_MeasureOverride(FrameworkElement element, Size availableSize)
  at System.Windows.FrameworkElement.MeasureOverride(Size availableSize)
  at System.Windows.FrameworkElement.MeasureOverride(IntPtr nativeTarget, Single inWidth, Single inHeight, Single&amp; outWidth, Single&amp; outHeight)
  at MS.Internal.XcpImports.MeasureOverrideNative(IntPtr element, Single inWidth, Single inHeight, Single&amp; outWidth, Single&amp; outHeight)
  at MS.Internal.XcpImports.FrameworkElement_MeasureOverride(FrameworkElement element, Size availableSize)
  at System.Windows.FrameworkElement.MeasureOverride(Size availableSize)
  at Microsoft.Phone.Controls.Panorama.MeasureOverride(Size availableSize)
  at System.Windows.FrameworkElement.MeasureOverride(IntPtr nativeTarget, Single inWidth, Single inHeight, Single&amp; outWidth, Single&amp; outHeight)
  at MS.Internal.XcpImports.MeasureOverrideNative(IntPtr element, Single inWidth, Single inHeight, Single&amp; outWidth, Single&amp; outHeight)
  at MS.Internal.XcpImports.FrameworkElement_MeasureOverride(FrameworkElement element, Size availableSize)
  at System.Windows.FrameworkElement.MeasureOverride(Size availableSize)
  at System.Windows.FrameworkElement.MeasureOverride(IntPtr nativeTarget, Single inWidth, Single inHeight, Single&amp; outWidth, Single&amp; outHeight)
  at MS.Internal.XcpImports.MeasureOverrideNative(IntPtr element, Single inWidth, Single inHeight, Single&amp; outWidth, Single&amp; outHeight)
  at MS.Internal.XcpImports.FrameworkElement_MeasureOverride(FrameworkElement element, Size availableSize)
  at System.Windows.FrameworkElement.MeasureOverride(Size availableSize)
  at Microsoft.Phone.Controls.PhoneApplicationFrame.MeasureOverride(Size availableSize)
  at System.Windows.FrameworkElement.MeasureOverride(IntPtr nativeTarget, Single inWidth, Single inHeight, Single&amp; outWidth, Single&amp; outHeight)
  </code></pre>
  
  <p>The debugging output contains:</p>
  
  <pre><code>A first chance exception of type 'System.ArgumentNullException' occurred in mscorlib.dll (x10)
  A first chance exception of type 'System.NotImplementedException' occurred in System.Windows.dll (x6)
  </code></pre>