Fix 'Type or namespace name not found' error in C# - Duplicate solutions

If you're encountering the "Type or namespace name not found" error in your C# project, there are several potential solutions to try. One common solution is to check your project's references and ensure that all necessary libraries are properly included. However, if you've already checked your references and are still seeing the error, it could be due to duplicate solutions in your project.

To fix this issue, you can try the following steps:

1. Open your solution in Visual Studio and navigate to the Solution Explorer.
2. Expand the solution and look for any duplicate projects or files.
3. If you find duplicates, right-click on them and select "Remove".
4. Build your solution again and see if the error persists.

Another potential solution is to clean and rebuild your solution. To do this, follow these steps:

1. Navigate to the Build menu in Visual Studio.
2. Select "Clean Solution".
3. Once the cleaning process is complete, select "Rebuild Solution".
4. Check if the error has been resolved.

If neither of these solutions work, it's possible that the error is being caused by a conflict between different versions of a library. In this case, you may need to manually edit your project file to remove any conflicting references.

To do this, open your project file in a text editor and search for the name of the conflicting library. Once you've found it, remove any references to older versions of the library and ensure that the correct version is included.

By trying these solutions, you should be able to resolve the "Type or namespace name not found" error in your C# project.