### *Fix*: Update to the latest version of Visual Studio 2017 - 15.9.19+

[![enter image description here][1]][1]

It appears this was only a problem for `.vbproj` project types. 

This was also reported in:

* the [dotnet/project-system github repo issues](https://github.com/dotnet/project-system/issues/4751)
* this Developer Community issue on the [Project Properties Build Page Blank](https://developercommunity.visualstudio.com/content/problem/460020/project-properties-build-page-blank.html)




  [1]: https://i.stack.imgur.com/RFrrw.png

When trying to open the Properties of a WPF application, on the Application page, it gives the following error: 

> An error occurred trying to load the page. The method or operation is not implemented.

[![screenshot][1]][1]

In the Windows Event Viewer I  can find this:

```none
Error Information 
AppInsightsEvent Name = vs/ml/proppages/appdesigner/prop-page-designer-view-fault
Description           = ActivatePage
TelemetrySession      = '4a288b83-00d2-4f45-84cf-513352811580' Started = True OptIn=True IsInitialized = True Cloned = False
WatsonEventType       = VisualStudioNonFatalErrors2
UTC time              = 2019-03-07T10:27:40

Exception:  System.NotImplementedException  
The method or operation is not implemented. 

Microsoft.VisualStudio.Editors.PropertyPages.WPF.ApplicationPropPageVBWPF.StartupObjectOrUri.GetHashCode()
System.Collections.Hashtable.GetHash(Object key) 
System.Collections.Hashtable.InitHash(Object key, Int32 hashsize, UInt32& seed, UInt32& incr) 
System.Collections.Hashtable.ContainsKey(Object key) 
System.Windows.Forms.ComboBox.ComboBoxItemAccessibleObjectCollection.get_Item(Object key) 
System.Windows.Forms.ComboBox.ComboBoxUiaProvider.SetComboBoxItemSelection()
System.Windows.Forms.ComboBox.OnSelectedIndexChanged(EventArgs e) 
System.Windows.Forms.ComboBox.set_SelectedIndex(Int32 value) 
System.Windows.Forms.ComboBox.set_SelectedItem(Object value) 
Microsoft.VisualStudio.Editors.PropertyPages.WPF.ApplicationPropPageVBWPF.SetSelectedStartupObjectOrUriIntoCombobox(ComboBox combobox, StartupObjectOrUri startupObjectOrUri) 
Microsoft.VisualStudio.Editors.PropertyPages.WPF.ApplicationPropPageVBWPF.SetStartupObjectOrUriIntoUI(Control control, PropertyDescriptor prop, Object value) 
Microsoft.VisualStudio.Editors.PropertyPages.PropertyControlData.InitPropertyUI()
Microsoft.VisualStudio.Editors.PropertyPages.PropPageUserControlBase.InitPage()
Microsoft.VisualStudio.Editors.PropertyPages.PropPageUserControlBase.SetObjects(Object[] objects) 
Microsoft.VisualStudio.Editors.PropertyPages.PropPageUserControlBase.IPropertyPageInternal_SetObjects(Object[] objects) 
Microsoft.VisualStudio.Editors.PropertyPages.PropPageBase.Create(IntPtr hWndParent) 
Microsoft.VisualStudio.Editors.PropertyPages.PropPageBase.IPropertyPage2_Activate(IntPtr hWndParent, RECT[] pRect, Int32 bModal) 
Microsoft.VisualStudio.Editors.PropPageDesigner.PropPageDesignerView.ActivatePage(IPropertyPage PropPage)
```

## What I've Tried

* I previously installed the Visual Studio 2019 RC, but have now uninstalled it. That version also gave the same error.  
* Reinstalling Visual Studio 2017 didn't help.
* This happens in old and freshly created projects.
* My coworker doesn't have this on his computer with the same projects.
* I did not have any problems last week. I haven't installed/uninstalled anything special.


  [1]: https://i.stack.imgur.com/wX0uB.png