Unable to open a windows form in visual studio community 2026/ visual basic

Hi @Dave Willadsen ,

Thanks for reaching out.

From my research, this kind of error is caused by the WinForms designer holding onto an old cached package path, even when that preview package was not intentionally added to the project.

The first thing I would do is close Visual Studio completely, then delete the WinForms designer cache under %LOCALAPPDATA%\Microsoft\VisualStudio\18.0_*\WinFormsDesigner. After that, delete the project's bin and obj folders, reopen the solution, and build again before opening the form.

It would also be worth checking the project file and packages.config if you have one, just to make sure Microsoft.Extensions.DependencyInjection.Abstractions is not explicitly referenced as a preview version. If you do find it there, remove it or change it to a stable release that matches the rest of the project, then restore and rebuild.

If Visual Studio still tries to pull that old package path back in, clear the NuGet caches as well with dotnet nuget locals all --clear, then restore again and test the designer one more time.

If there is no preview reference anywhere in the project after that, then this points more to a Visual Studio designer cache or tooling issue. In that case, I would update Visual Studio to the latest servicing build and, if needed, use the Visual Studio Installer to repair the .NET desktop development workload so the Windows Forms designer components are refreshed as well.

Hope this helps! If my explanation and the information I provided were helpful, I would greatly appreciate it if you could follow the instructions here so others with the same problem can benefit as well.

Hi Dave Willadsen,

As per my understanding may be windows forms corrupted so please re-install windows forms from VS installer then try again.

Thanks.

The error indicates that the Windows Forms designer is trying to load a preview NuGet package assembly from a cached path that no longer exists or is invalid:

Microsoft.Extensions.DependencyInjection.Abstractions.8.0.0-preview.7.23375.6

To restore the designer:

1. Clean and rebuild the project
   1. In Solution Explorer, right‑click the solution or project and select Clean.
   2. Right‑click again and select Rebuild.
   3. Try reopening the form in the designer.
2. Clear build artifacts
   1. Close Visual Studio.
   2. In File Explorer, delete the bin and obj folders in the project directory.
   3. Reopen the solution and build again, then open the form designer.
3. Remove the preview package from the project
   1. In Visual Studio, open Project > Manage NuGet Packages.
   2. Locate Microsoft.Extensions.DependencyInjection.Abstractions.
   3. Either:
      • Downgrade to a stable version that matches the rest of the solution, or
      • Remove the package if it is not required.
   4. Build the project again and reopen the form designer.
4. If the problem persists
   • Use Help > Send Feedback > Report a Problem in Visual Studio to submit the issue, including the full error text and steps to reproduce. This sends diagnostic data that can help identify if the designer cache under %LOCALAPPDATA%\Microsoft\VisualStudio\18.0_*\WinFormsDesigner is corrupted and needs product-side fixes.

If the designer continues to fail after these steps and the preview package is no longer referenced in the project, include that detail when reporting the problem so it can be prioritized appropriately.

References:

• Windows Forms Designer error page
• Report a problem with the Visual Studio product or installer