WinForms Designer cannot design From inheriting from another Form

• .NET Core Version:

.NET SDK (reflecting any global.json):
 Version:   5.0.100
 Commit:    5044b93829

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.17134
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\5.0.100\

Host (useful for support):
  Version: 5.0.0
  Commit:  cf258a14b7

.NET SDKs installed:
  5.0.100 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.NETCore.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

• VS: 2019 16.9 Preview 1 Community

• Have you experienced this same bug with .NET Framework?: No. On .Net Framework in the same VS version it works quickly and flawlessly.

Problem description:

Not sure if it is related to VB or is also applicable to C#, but I have the case:

FormIWantToDesign.vb

Friend Class FormIWantToDesign : Inherits ContainerForm

End Class

FormIWantToDesign.Designer.vb

<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Class FormIWantToDesign : Inherits ContainerForm

End Class

ContainerForm.vb

Public Class ContainerForm : Inherits System.Windows.Forms.Form

End Class

ContainerForm.Designer.vb

<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Class ContainerForm
    Inherits System.Windows.Forms.Form
'Designer generated code here
End Class

All classes / files are part of the same .Net 5 project. Project compiles, is built, rebuilt, and at runtime everything works.

Expected Behavior: When I click on FormIWantToDesign.vb I want the VS to show me a WF designer so I can interact with controls on the form, just as is the case with .Net Framework version of it.

Actual Behavior:

The designer could not be shown for this file because none of the classes within it can be designed. The designer inspected the following classes in the file: The designer could not be shown for this file because none of the classes within it can be designed. The designer inspected the following classes in the file: \r\n FormIWantToDesign --- The base class 'MyProjectNamespace.ContainerForm' could not be loaded. Ensure the assembly has been referenced and that all projects have been built.     

Instances of this error (1)  
 
at Microsoft.VisualStudio.WinForms.RemoteClient.Loader.RemoteCodeDomDesignerLoader.EnsureDocument(IDesignerSerializationManager manager)
at Microsoft.VisualStudio.WinForms.RemoteClient.Loader.RemoteCodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager manager)
at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager serializationManager)
at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.DeferredLoadHandler.Microsoft.VisualStudio.TextManager.Interop.IVsTextBufferDataEvents.OnLoadCompleted(Int32 fReload)  

Why it says MyProjectNamespace.ContainerForm cannot be loaded I have no idea. The project has been built, and is the same project as the one that contains the form I try to open in a designer.

Minimal repro: See files samples above.

[kirsan31]

The RuntimeIdentifier may be used beyond publishing, maybe the VS designer is running 64 bit and setting the RuntimeIdentifier conflicts? Just a random guess.

Yes, there was an issue about that. @fitdev I am worry if you will have both RuntimeIdentifier and Platforms - will it work? Also we have https://github.com/dotnet/sdk/issues/1553 😃

[dsplaisted]

I believe you can also set up publish profiles which can specify the RuntimeIdentifier to use for publish.