conflicting extension methods : Extension « Class « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. Class
3. Extension

using System;

    public static class ExtensionMethods
    {
        public static string Substring(this string s, int startIndex, int endIndex)
        {
            if (startIndex >= 0 && startIndex <= endIndex && endIndex < s.Length)
                return s.Substring(startIndex, endIndex - startIndex);
            else
                return s;
        }
    }

    public class Tester{
        public static void Main()
        {
            string hello = "Hello";
            Console.WriteLine("hello.Substring(2, 3) = {0}", hello.Substring(2, 3));
        }
    }