wat

So in C++ I could do

class A {
    int B();
}

int A::B()
{
    return 1;
}

i.e. I could keep my class definition and the code for the methods separate, but I can't figure out how to do the same thing in C#.  Do I really have to use "partial class A {}" in front of everything?

There is no reason to keep class definitions and code separate. It's a holdover from the days of K&R where compile times where actually a problem and all compilers were single pass.