An object-oriented and type-safe programming language that has its roots in the C family of languages and includes support for component-oriented programming.
Thanks for reaching out.
This error is from the WinForms out-of-process designer (Microsoft.DotNet.DesignTools…). It can appear even when the project builds, because the designer uses a separate design-time build and caches/shadow-copy folders.
Try the following (in order):
- Close Visual Studio and delete your project’s bin and obj folders.
- Delete the WinForms designer cache:
%LOCALAPPDATA%\Microsoft\VisualStudio\17.*\WinFormsDesigner - Reopen VS, restore NuGet packages, then Rebuild the solution.
- Enable designer logs: Tools → Options → Windows Forms Designer → set Logging Level to Verbose, then open the form and check Output → Windows Forms for the real root cause.
Let us know if the issue persists after following these steps. I’ll be happy to assist further if needed. If the issue has been resolved, Kindly mark the provided solution as "Accept Answer", so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.