in operator in C#

Question

I think there was an in operator in Commodore 128 Basic.
Is there an in operator in c# too?

I mean is there an operator of kind

if(aString in ["a", "b", "c"])  
  Console.Out.WriteLine("aString is 'a', 'b' or 'c'");

Edit1: Currently I need it to decide if an enum value is in a range of some enum values.

Edit2: Thank you all for the Contains() solutions. I will use it in the future. But currently I have a need for enum values. Can I replace the following statement with Contains() or other methods?

public enum MyEnum { A, B, C }

class MyEnumHelper
{
  void IsSpecialSet(MyEnum e)
  {
    return e in [MyEnum.A, MyEnum.C]
  }
}

Edit3: Sorry it was not Basic. I just googled a while and found Turbo Pascal as a candidate where I could saw it. See http://en.wikipedia.org/wiki/Pascal_%28programming_language%29#Set_types

Edit4: Best answers up to now (end of 15 Feb 2012):

• For lists and arrays: accepted answer and all other answers with Contains() solutions
• For Enums: TheKaneda's answer with good list of pros/cons for different extension methods

Answer 1

Try this:

if(new [] {"a", "b", "c"}.Contains(aString))  
    Console.Out.WriteLine("aString is 'a', 'b' or 'c'");

This uses the Contains method to search the array for aString.