What are the most common naming conventions in C# for classes, namespaces and methods? Is it common to have getter/setter style methods as in Java?
No it is not common to use getter /setter style names in C#. Properties should be used for almost all places you would use a getter / setter in Java.
IMHO, the defacto standard for naming conventions comes from the Framework Design Guidelines. It's enforced by several tools (FxCop) and is the dominant style of many libraries including the BCL.