The joy of Extension Methods in C# 3.0

I discovered a new addition to C# 3.0 called Method Extension while I was writing a convertor for Hex and Binary for Cosmos today. Method Extension is a technique for "spot-welding" methods on to existing classes or types.

    //Without C# 3.0 Method Extension

    if (IsOdd(7))

        ;

    //With C# 3.0 Method Extension

    if (7.IsOdd())

        ;

Here the I've added the IsOdd method onto an integer type. I think the lower example is a lot easier to read than the upper.

Adding an extended method is as simple as adding 'this' keyword on the first parameter on a static method inside a static class, like this:

    public static class IntExtender

    {

        /// 

        /// Checks if number is odd or even.

        /// 

        public static bool IsOdd(this int n)

        {

            if ((n % 2) > 0)

                return true;

            else

                return false;

        }

    }

Method Extensions requires a reference to System.Data.Core assembly in your project.

The Intellisense looks like this:

By adding extensions in Cosmos we can now directly convert numbers to Hex and Binary like this:

    foreach (byte b in bytes) 

    {

        Console.Write(b.ToBinary());

        Console.Write(b.ToHex());

    }