Custom ASMX Could not create type

I was trying to add my own WebService/asmx to SharePoint 2013.

and I got this wonderful error message

Sorry, something went wrong

An error occurred during the processing of /_layouts/MyFolder/MyWS.asmx. Could not create type 'MyNamespace.MyClassName'.

Technical Details

Troubleshoot issues with Microsoft SharePoint Foundation.

Correlation ID: 93a3de9c-2213-3030-a6c5-f324a2c11743

Date and Time: 1/11/2015 10:11:35 AM

BTW, it was working on SharePoint 2007 with the same method which I've also seen to be working here:

1. I've compiled my WebService Against .Net 4.0 (AnyCpu) to get MSIL DLL file.


2. Copied the files to SharePoint machine


3. 
   

   Installed to GAC by using this:

   
   

   C:\Program Files (x86)\Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools\x64\gacutil.exe -I MyDllName.dll

   
   


4. 
   

   Tested that the Dll were successfully installed by using this:

   
   

   C:\Program Files (x86)\Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools\x64\gacutil.exe -L MyDllName.dll

   
   


5. 
   

   I've also tried to write text-only asmx to test the GAC:

   
   

    <%@ WebService language="C#" class="TestMyAssembly" %>



  using System;
  using System.Reflection;
  using System.Web.Services;
  using System.Xml.Serialization;

  [WebService(Namespace = "http://test.com/Test")]
  public class TestMyAssembly : WebService
  {
      [WebMethod]
      public String TestAssembly()
      {

        Assembly assembly1 = Assembly.Load("FullAssemblyName1, Version=1.0.0.0,     Culture=neutral, PublicKeyToken=118db1178ce8ee11, processorArchitecture=MSIL");


        Assembly assembly2 = Assembly.Load("FullAssemblyName2, Version=1.0.0.0,     Culture=neutral, PublicKeyToken=22e5225e223b2240, processorArchitecture=MSIL");

        if (assembly1 != null && assembly2 != null)
        {   
            return "No exception so far...";
        }

        return "Something is wrong";
      }
  }
 

Any help would be greatly appreciated. thanks!