.net8 windows form design view problem.

Ahmet Haluk UZUNER 20 Reputation points

I am developing Revit addin in Vidual Studio in c++/cli as class library.

Before moving to .net platform everyhing was working fine. But in .net Windows form design views doesnt work. Though when I add form element by code. It compiles and works.

The error is:

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: ModelessForm --- The base class 'System.Windows.Forms.Form' could not be loaded. Ensure the assembly has been referenced and that all projects have been built.

Regarding to Windows forms I aded lines below to .vcxproj file




<FrameworkReference Include="Microsoft.WindowsDesktop.App" />

<FrameworkReference Include="Microsoft.WindowsDesktop.App.WPF" />

<FrameworkReference Include="Microsoft.WindowsDesktop.App.WindowsForms" /> </ItemGroup>

Instances of this error (1)

  1. Hide Call Stack

at System.ComponentModel.Design.Serialization.CodeDomDesignerLoader.EnsureDocument(IDesignerSerializationManager manager)

at System.ComponentModel.Design.Serialization.CodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager manager)

at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager serializationManager)

at System.ComponentModel.Design.Serialization.BasicDesignerLoader.BeginLoad(IDesignerLoaderHost host)

This is form design view window.2024-05-04 21 56 39

2024-05-04 21 58 12 The Visual Studio project file is at link below.


Does snybody have any idea how i can resolve that problem?

Visual Studio
Visual Studio
A family of Microsoft suites of integrated development tools for building applications for Windows, the web and mobile devices.
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A high-level, general-purpose programming language, created as an extension of the C programming language, that has object-oriented, generic, and functional features in addition to facilities for low-level memory manipulation.
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Accepted answer
  1. Minxin Yu 10,361 Reputation points Microsoft Vendor


    In Configuration Manager: add new configuration. Such as named design , used to design Winform but not compile it.

    User's image Then
    User's image

    Click OK. Then CTRL+S to save the project file.

    Add the condition to vcxproj file reference include and framework reference

    enter image description here


    In Design:

    User's image

    Since out of process does not support C++CLI. You still need to add controls' code manually, but the controls can be displayed in the designer.

    Before building the project, switch to Debug or Release.

    Best regards,

    Minxin Yu

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