Whatever blows your hair back

This morning I was working on some legacy code (code I find that has no corresponding unit tests assigned to it) and found myself wanting the C# equivalent of the SQL “NOT IN” and “IN” statements. For example,

SELECT COUNT(*) FROM
WHERE NOT IN { }

So, I wrote a simple little extension method class to do just that:

static public class Extensions
{
	static public bool IsIn(this Int32 value_, params Int32[] list_)
	{
		// LINQ is less efficient...
		// return list_.Where(v => { return v == value_;}).Count() > 0;
		// ...than this:
		foreach (var value in list_)
			if (value == value_)
				return true;

		return false;
	}
	static public bool NotIn(this Int32 value_, params Int32[] list_)
	{
		return !IsIn(value_, list_);
	}
}

Now you can write code like this:

public void Example1 (Int32 [] someList_)
{
   if (5.IsIn(someList_)
      DoSomethingSexy();
}

… or like this:

public void Example2 (Int32 value_)
{
   if (value_.NotIn(_myList))
      DoSomethingElseSexy();
}

Enjoy!