Question

In C# if I want to see if a variable is equal to one of a set of fixed values, I currently do this…

bool result = ( (x==MyEnum.A) || (x==MyEnum.B) || (x==42) );

…which to me is cumbersome. Is there anything similar to this pseudo-code?

bool result = x in {MyEnum.A, MyEnum.B, 42};

I know I can create an array inline with the values, then use LINQ across that, but are there any other options?

Answer 1

This is probably a BAD idea, but you can turn Contains on its head and get syntax similar to what you ask in your question with a new extension method:

//Generic.  All items in the set and the candidate must be the same type.
public static bool In<T>(this T item, params T [] set)
{
  return set.Contains(item);
}

bool result = x.In(MyEnum.A, MyEnum.B, MyEnum.C);

//Non-generic and non-typesafe.  Anything goes.  Use with care!
public static bool In(this object item, params object [] set)
{
  return set.Contains(item);
}


bool result = x.In(MyEnum.A, MyEnum.B, 42);

//int-specific.  
public static bool In(this int item, params int [] set)
{
  return set.Contains(item);
}


bool result = x.In((int)MyEnum.A, (int)MyEnum.B, 42);