C# in operator-overloading

Question

Hi,

I just had an idea last nigth when writing an if-expression and sometimes the expression tend to be long when you have it like this:

if(x == 1 || x == 2 || x == 33 || x == 4 || x == -5 || x == 61) { ... }

x can be enums,strings,ints,chars you get the picture.

I want to know if there are an easier way of writing this. I think of sql's operator 'in' for example as a eay to shorten the expression:

if(x in (1,2,33,4,-5,61)) { ... }

I know you can't write an expression like this with 'in' because the lexer and parser of the compiler won't recognize it.

Perhaps other solutions as extension methods of different types of x is the solution? In the coming .NET 4.0 i heard something about parameterized methods, should that solve the n amount of parameters supplied to the if-expression ?

Perhaps you understand me, have you an idea of a good practice/solution to this question?

/Daniel

Answer 1

Try the following

if ( (new []{1,2,33,4,-5,61}).Any(i => x == i) ) {
  ...
}

Answer 2

   string[] possible = new string[3] { 1, 2, 3);

   if (possible.Contains(x)) { ...

Answer 3

    bool In<T>(T num, params int args)
    {
        return (new List<T>(args)).Contains(num);
    }

Answer 4

    public static bool In<T>(this T X, params T[] list)
    {
        foreach (var item in list)
        {
            if (X.Equals(item))
                return true;
        }
        return false;
    }

Answer 5

Given that x is an int you could write an extension method like so:

public static bool In(this int i, params int[] values){
    foreach(int v in values) {
        if (i == v) {
            return true;
        }
    }
    return false;
}

Answer 6

I usually write an Extension Method as follows:

public static bool In<T>(this T source, params T[] list)
{
  if(null==source) throw new ArgumentNullException("source");
  return list.Contains(source);
}

Which can be used like this:

if(x.In(1,6,9,11))
{
      // do something....
}