Switch statement without default when dealing with enumerations

Question

This has been a pet peeve of mine since I started using .NET but I was curious in case I was missing something. My code snippet won\'t compile (please forgive the forced nat

Answer 1

That's because the value of decision could actually be a value that is not part of the enumeration, for instance :

string s = GetDecision((Decision)42);

This kind of thing is not prevented by the compiler or the CLR. The value could also be a combination of enum values :

string s = GetDecision(Decision.Yes | Decision.No);

(even if the enum doesn't have the Flags attribute)

Because of that, you should always put a default case in you switch, since you can't check all possible values explicitly