Remove duplicate characters in a string

using System;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(RemoveDublicate("Devarajan"));
            Console.Read();
        }
        static string RemoveDublicate(string key)
        {
            string result = "";
            foreach(char value in key)
            {
                if(result.IndexOf(value) == -1)
                {
                    result += value;
                }
            }
            return result;
        }

    }
}