ExtensionExample.cs

using System;

namespace Theory10
{
    /// <summary>
    /// Class ExtensionExample defines the extension method
    /// </summary>
    static class ExtensionExample
    {
        // Extension Method to convert the fist character to          
        // lowercase
        public static string FirstLetterLower(this string result)
        {
            if (result.Length > 0)
            {
                char[] s = result.ToCharArray();
                s[0] = char.ToLower(s[0]);
                return new string(s);
            }
            return result;
        }
    }

    class Run
    {
        public static void Main(string[] args)
        {
            string country = "Great Britain";
            // Calling the extension method
            Console.WriteLine(country.FirstLetterLower());
        }
    }


}