Some project required me to port Java source code into .NET environment. I had to import this code into J# project and then compile it. It worked ok if you had entire source code but usually I did not have it or Java project used some third party JARs. Searching for some solution I found IKVM.NET This is a striking solution and it solves 99% of problems of usage Java in .NET. It converts Java byte code into .NET CLR and you do not need to any source code any more. It is amazing and many thanks to its author Jeroen Frijters.