How do you clear temporary files in an ASP.NET website project?

I have been building and rebuilding an ASP.NET program.

I made the horrible mistake, I think, of recently copying the published content back to the folder I was developing.

So now I have an unusual error when I build the code. It says That there is a duplicate definition in one file in a temporary directory with anohter file in a temporary directory.

Error 3 The type 'ChildEventHandler' exists in both 'c:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files...\b90cc7a4\28d266b\assembly\dl3\c4cf1ea3\b6e4b808_ef7cce01\App_Code.DLL' and 'c:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files...\b90cc7a4\28d266b\App_Code.asx5jp5d.dll' C:\inetpub\wwwroot...\Resources\usercontrols....ascx.cs 11 18 C:......\

I removed project and file names, of course, but this is basically what the error says.

Since the error is with temporary files, what should I do?

I do not see a "clear" option in visual studio to clear out the files of a compile.