Python 'in' operator equivalent in C# (.NET 2.0)

Question

I love pythons in-operator and I would like to write it and use it in a c# project. I only have access to .NET Framework 2.0 . I am using the code below but I don't understand the compile error.

using System;
using System.Collections.Generic;
using System.Text;

public static bool In<T>(this T item, IEnumerable<T> sequence) {
    if (sequence == null)
        throw new ArgumentNullException("sequence");

    return sequence.Contains(item);
}

I also have a reference to System as well, but I get the following compile error:

'System.Collections.Generic.IEnumerable<T>' does not contain a definition for 'Contains' and no extension method 'Contains' accepting a first argument of type 'System.Collections.Generic.IEnumerable<T>' could be found
(are you missing a using directive or an assembly reference?)

I don't understand what reference I might be missing!

EDIT:

Seems like there is no Linq in .NET framework 2.0. So I downloaded and used the following package: http://www.albahari.com/nutshell/linqbridge.aspx it includes a namespace System.Linq which solves the compile error.

I want to test it with the following code:

char[] x = { 'a', 'b', 'c' };
if('a'.In(x))
{
    ;   
}

But I get confusing errors:

'char' does not contain a definition for 'In' and no extension method 'In' accepting a first argument of type 'char' could be found
(are you missing a using directive or an assembly reference?)

EDIT: A clean built solved the issues.

Answer 1

The Contains static method is defined inside System.Linq .

If you add the line using System.Linq; at the top of your file, your code should compile.

Incidentally, isn't the Contains method identical to Python's 'in' operator? You don't really gain much from creating a custom method, except that you get to type a few less characters/get to reverse the operands.

If you're using .NET 2.0, you might be able to adapt one of the methods in this SO post in lieu of using Linq.