While it feels a bit hacky and unclean, you may want to try using IKVM (http://www.ikvm.net/) to translate and import the Java client in to your .NET project.

Given the difficulty in building a client period (distributed systems, race conditions, etc), being able to rely on the widely adopted & supported official client is quite attractive.

In my test cases the performance is on par running natively on the JVM, except when compression is enabled.

Another option is using the REST proxy and accepting the trade-offs that imposes.