Use WPF DLL Assembly in ASP.NET problem

I have C++ project that compiles as DLL Assembly in .NET 3.5 SP1 Project is used for Image rendering processing by using WPF (it loads 2 images from local folder, applies one image on another and saves the output file in the same folder). I want to use that that project as a reference in ASP.NET project to the rendering on the website. So I created simple Web Project in ASP.NET C# that uses C++ project as a Reference. Everything works great in ASP.NET Web Development Server (built-in Web server in VS2008). But once I publish this project to IIS on the same Machine or use IIS for debug instead of built-in Web server Image rendering it's not working anymore. I'm not getting any exceptions or error messages, it just output image is not processe开发者_开发技巧s as it supposed to be.

If anyone know what could cause that I would really appreciate your insight!

Do you have access to the Event Logs? You should check there for any errors. You should try to throw an exception from a C#-only code path and make sure that everything is OK and regular exceptions are being thrown. Is the C++ compiled to managed code, or is native code? You might find that ASP.NET does not have the appropriate code access security permissions and needs to be registered in the GAC of the server to accessed from C#.

You should also check whether the DLL is thread-safe. This has caused issues for other users in ASP.NET/IIS.