Jon Skeet has an in-depth explanation of how to improve the performance of code that needs to dynamically invoke methods through reflections.
The bottom line is that if you have performance sensitive code that needs to invoke methods that you fetch from reflection, you should avoid using MethodInfo.Invoke() and instead create a delegate from the MethodInfo, and perform the invocations that way:
[...]Using a delegate invocation is only about 10% slower than direct invocation, whereas using reflection takes over 600 times as long. Of course these figures will depend on the method being called - if the direct invocation can be inlined, I'd expect that to make a significant difference in some cases.
This is a well-known trick, but Jon provides a great exploration of the subject.
Protocol Buffers for .NET
Additionally, you can see that Jon's effort to port Google's Protocol Buffers to C# are almost complete.
There are currently three separate approaches to support Protocol Buffers in .NET. Jon's effort essentially mimics the existing support for C# and integrated with the Google implementation and compilers. The other efforts have taken slightly different approaches, one of them is designed with the WCF approach in mind: use C# classes/interfaces as the actual public contract, as opposed to the .proto files.