Missing DLL on Bin folder

Error:

Microsoft Visual Studio 20120

Compiler Error Message: CS0433: The type ' ??' exists in both 'c:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\f4d18c32\7ff7a684\assembly\dl3\22b261c4\d7cf8f46_c3cbcd01\??.DLL'

 and 

'c:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\f4d18c32\7ff7a684\assembly\dl3\df9ab059\43217199_27cecd01\??.DLL'


Solution:

Remove the problematic DLL from WEB\bin.