WebProxy

using System;
using System.Net;
using System.IO;
using System.Linq;
using System.Text;

class Program
{
    static void Main()
    {
        WebProxy p = new WebProxy("192.178.10.49", 808);
        p.Credentials = new NetworkCredential("username", "password");
        // or:
        // p.Credentials = new NetworkCredential("username", "password", "domain");

        WebClient wc = new WebClient();
        wc.Proxy = p;
    }

}