I'm holding a public Essential Test-Driven Development course at the end of September, through Agile Learning Labs. Chris Sims and I separated this one, and another in December, by programming language: September's is in C#, and December's is in Java.
I've held a number of "multilingual" public TDD courses in the past, and they tend to go very well for everyone. The languages are similar enough, and I always carry the coding samples for all the available course languages.*
The techniques, exercises, and tools are so similar that people can transition back and forth between Java and C# quite easily. Often lab partners will pair up with others using a different IDE or language, in order to get a taste for those environments. There may not be any better way to learn a language than to explore its capabilities using a lightweight testing framework and a Test-Driven approach.
Also, I've noticed repeatedly since first trying out TDD in 1998 that the selection of language or IDE is not the limiting constraint when using Test-Driven Development to build high-quality, high-value software.
So if you're a Java developer who would really rather take the September course, or a C# developer who prefers the December schedule, don't hesitate. You won't be slowing anyone down, and you won't be hindered by much. There's a chance you'll be spending part of the time pair-programming on an IDE that you're not familiar with, but you and your lab partner can switch IDEs on another exercise.
You can use discount code RobReferral at either course for an additional $300 off. I hope to see you there!
(* Essential Test-Driven Development can be provided in C++, C#, Java, or VisualBasic.Net. In the C++ and VB.Net TDD courses, I cover language-specific idioms and techniques. If you are primarily a C++ or VB.Net developer, let us know of your interest and we'll give you some options to attend a course in the programming language of your choice.)