Question

I know this sort of code is not best practice, but nevertheless in certain situations I find it is a simpler solution:

if (obj.Foo is Xxxx)
{
   // Do something
}
else if (obj.Foo is Yyyy) 
{
   // Do something
}
else
{
    throw new Exception("Type " + obj.Foo.GetType() + " is not handled.");
}

Anyone know if there is a built-in exception I can throw in this case?

Answer 1

If obj is an argument to the method, you should throw an ArgumentException:

throw new ArgumentException("Type " + obj.Foo.GetType() + " is not handled.", "obj");

Otherwise, you should probably either throw an InvalidOperationException or create your own exception, like this:

///<summary>The exception thrown because of ...</summary>
[Serializable]
public class MyException : Exception {
    ///<summary>Creates a MyException with the default message.</summary>
    public MyException () : this("An error occurred") { }

    ///<summary>Creates a MyException with the given message.</summary>
    public MyException (string message) : base(message) { }
    ///<summary>Creates a MyException with the given message and inner exception.</summary>
    public MyException (string message, Exception inner) : base(message, inner) { }
    ///<summary>Deserializes a MyException .</summary>
    protected MyException (SerializationInfo info, StreamingContext context) : base(info, context) { }
}