Consider the following example of a simple enum and a switch over all possible enum values.

enum State { Alpha, Beta, Gamma }

State state = ...;

switch(state) {
case Alpha: ... break;
case Beta: ... break;
case Gamma: ... break;
}

Now I get error CS0161: not all code paths return a value.

This seems rather pointless to me, because I would expect that other cases are not possible. So what is the purpose of this error, and how would one work around this in the most elegant way?