如何让HttpWebRequest使用指定网络接口传输数据

using System;
using System.Net;

class Program
{
public static void Main ()
{
foreach (var ip in Dns.GetHostAddresses (Dns.GetHostName ()))
{
Console.WriteLine ("Request from: " + ip);
var request = (HttpWebRequest)HttpWebRequest.Create ("http://ns1.vianett.no/");
request.ServicePoint.BindIPEndPointDelegate = delegate {
return new IPEndPoint (ip, 0);
};
var response = (HttpWebResponse)request.GetResponse ();
Console.WriteLine ("Actual IP: " + response.GetResponseHeader ("X-YourIP"));
response.Close ();
}
}
}