I thought I'd spread the word about a useful, but not that well-known operator in C#; the null-coalescing operator ??.

This is what the C# Language Reference has to say about the operator:

"The null-coalescing operator is used to define a default value for a nullable value types as well as reference types. It returns the left-hand operand if it is not null; otherwise it returns the right operand."

What this means is that instead of doing:

if (x == null)
    return -1;
else
    return x;

You can do:

return x ?? -1;