32bit dll not loading with Enable32Mode on IIS 7.5

Question

I have a MVC 3 Web Site referencing a 32 bit DLL. The OS is Windows 2008 R2 x64. The website is in the ASP.NET 4 App Pool. I have turned on Enable32Bit but it doesn't work. I get a Bad Image Exception but can't find out to turn this level of logging on in IIS. I have setup up a page that outputs whether it's running 32bit or 64bit and when I turn on/off the Enable32Bit on the AppPool I get the correct output. The website is also in Full Trust.

I'm at a loss to try and and get it to work. I do know that it works on Win7 32bit.

Can you suggest some things to try?

UPDATE: I have just written a simple Windows Forms App with a button on it which calls my DLL. This was built with target of x86 and it worked fine so there is an issue with IIS or ASP.Net I think. Here is the code that is being used to reference the DLL:

        [DllImport("CDCrypt.dll")]
        [return: MarshalAs(UnmanagedType.LPStr)]
        public static extern String Encrypt([MarshalAs(UnmanagedType.LPStr)] String aName);



        [DllImport("CDCrypt.dll")]
        [return: MarshalAs(UnmanagedType.LPStr)]
        public static extern String Decrypt([MarshalAs(UnmanagedType.LPStr)] String aName);

UPDATE 2: Does it matter if the ASP.Net Pipeline is Clasic or Integrated? I've tried both but same problem but thought it was worth asking

UPDATE 3: I found this question trying to do the same thing and he gave up which isnt too helpful!!

Answer 1

Make sure that all the managed assemblies are targeting x86 instead of Any CPU or x64 in the properties of the project.