This has nothing to do with the development tool, but your winform project is configured incorrectly. Please ensure that your project resource file has been compiled and generated correctly (Resources.resx file under the property). The "or" prompt in the second half of the screenshot refers to the application set signature, as shown in screenshot 2. The most convenient thing is to delete the Resources.resx file under the root directory attribute, or open it yourself.

Modify the namespace of a resource. The Designer.cs file should be caused by modifying the "default namespace" of the project (incomplete modification). Ensure that the Resources.resx file under Properties is compiled correctly, and the namespace must be consistent with the current project, and then right-click? Solution explorer? Project name, first clean up (or delete the root directory obj compilation temporary folder yourself) and then regenerate.

For your assembly name "windowsApplication 1", it is really impossible to rebuild a solution of the winform project, and then copy the existing form file into the new project for recompilation. I have just been in contact with VS for 3 days, and I don't know how to explain it to you. ...