Re: .net to java converter ?
I looked for one for ages, but there just isn't one that's survived the test of time. Loads of third party and open source stuff that long withered and died. In the end I ended up going down the Java JNI -> C++ -> Managed C++ -> C# route, which is fiddly but at least it's all mine.
It was fiddlier on Linux unfortunately, cos mono's handling of the managed / unmanaged code transition is unpleasantly like JNI. At some point we'll have to jump ship to .NET Core I expect, but I'll leave it til the last minute.
IKVM for going the other way is awesome, but Jeroen Frijters has said he's no longer updating it, so it's stuck at Java 8. In the ideal world, it being open sourced, someone would take this on......