Cannot add file to solution: "A file or folder with the name [name] already exists"

When I attempt to add any file to my project, I get this error: A file or folder with the name azazaz.cs already exists. Please give a unique name to the item you are adding, or delete the existing item first.' There have been no updates to Visual Studio recently. The problem only occurs in this one project. It works properly on other computers. What I've tried so far: I tried many different names, checked for hidden files, and checked the folder location. Deleted the repository and downloaded again (through GitHub), as suggested by AbhishekP. Deleted the "ComponentModelCache" folder in "AppData\Local" folder as suggested by Srikanth. Checked the ".csproj" folder for the file name in the error message, but it doesn't exist. I can't really start over and create a new project.