How to fix this window form issue?

Hi Chheng E Yeoum,

• first we need to understand any controls like button or combobox will placed and enabled any events from the controls then without cleared the events control will removed from the forms.
• suppose after enabled events controls removed this error message will popup.
• Just undo the action and clear events properly. then remove controls it will work.

Thanks.

Hello @Chheng E Yeoum ,

Thanks for your question.

The Windows Forms Designer cannot load Form1.cs even though the project has 0 Errors and 0 Warnings. This is a Designer-specific issue, not a project/code issue.

I recommend some following steps:

1. Rebuild the solution first. Then go to Build → Rebuild Solution, then try opening the Designer again.
2. Open the Designer through Solution Explorer. Instead of clicking the tab directly, right-click Form1.cs in Solution Explorer → select View Designer (or press Shift + F7).
3. Close and reopen the Designer tab — Close the Form1.cs [Design] tab completely, then reopen it via Solution Explorer as described above.
4. Check the project's target framework. The Windows Forms Designer works best with .NET Framework. If the project targets .NET 5/6/7+, make sure you are using Visual Studio 2022 which has better support for it.
5. Reopen via the .sln file. Close Visual Studio and reopen the project by double-clicking the .sln file (not the .cs file directly).

I hope this addresses your question. If this response was helpful, please consider following the guidance to provide feedback.

The Windows Form designer is failing to load and is showing the designer error page instead of the form surface. This happens when Visual Studio can’t parse or generate code for the form file inside the project.

Use these steps to fix it:

1. In Solution Explorer, confirm that Form1.cs, Form1.Designer.cs, and Form1.resx are all included in the same project (no “ghost” files under the solution root). If any of them are outside the project or shown as missing, remove them and re‑add them through Add > Existing Item….
2. Open Form1.Designer.cs and check that the partial class matches the main form file:
   • Same namespace as in Form1.cs.
   • Same class name (public partial class Form1 : Form).
3. Build the project. If there are any compile errors in the form or designer files, fix them first; the designer only loads when the code compiles.
4. Close the designer tab, then reopen the form by double‑clicking Form1 in Solution Explorer. If the designer still shows the error page, use the yellow error bar to jump to the exact line and file that’s blocking the designer and correct that code.

The designer error page is expected whenever there’s a code or project issue; once the underlying error is fixed, the normal Windows Form surface will appear again.

References:

• Windows Forms Designer error page