Extending With Extension Methods

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

namespace DripCode.Text
{
    public static class ExtensionMethods
    {
        public static Boolean ContainsAt(this string line, string template, int location)
        {
            return line.Contains(template) && line.Length >= template.Length + location && line.Substring(location, template.Length) == template;
        }
    }
}

Usage:

string Test = "hello world!"
Console.WriteLine(Test.ContainsAt("hello",0).ToString());
Console.WriteLine(Test.ContainsAt("world",6).ToString());

Extension Methods (C# Programming Guide)