Hi,
What type is your ASP.NET project, ASP.NET website or ASP.NET web application? If it is ASP.NET web application, please make sure the web application dll is in the Bin folder.
If ASP.NET cannot load its dll, the error will be thrown.
Please check the Output path is in application root Bin folder (Right click project name from Solution window, and enter its Properties Page and set its Output path in Build tab).
I look forward to receiving your test results.