Question

I’m using custom attributes to attach meta-data to class methods. During run-time, those attributes, and their parameters, are validated. Is there a consensus about what existing exception class to throw should an attribute (or attribute parameter) prove invalid?

For instance, given an attribute taking a instance method name as its constructor parameter:

public class StateAttribute : Attribute {
    public string ParentState { get; set; }
    public StateAttribute() {}
}

when used in a class like:

public StateMachine {
   [State]
   public Result TopState(Event e) { ... }

   [State( ParentState = "TopState" )]
   public Result NestedState(Event e) { ... }
}

An initialization routine will walk all the methods to which the State attribute has been applied, and resolve the ParentState name to the actual MethodInfo. If (eg. due to a typo) no method with that name can be found, it needs to throw an exception. Since I don’t want to invent new exception classes, which one would you suggest?

And just to be sure, there’s no way to validate the method names during compile time, right?

Answer 1

InvalidOperationException is the all-purpose one I personally use when “something has gone wrong”.

But to be honest, this sounds like a perfect case for deriving your own Exception to me.