ASP.NET获取客户端IP及MAC地址很多时候非常必要的，像做投票、留言、评论 等系统的时候防止别人恶意操作，导致数据的虚假行。下面介绍获取客户端的IP和MAC地址的方法，仅供参考：

获取客户端IP:

private string GetClientIP()
{
   string result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
   if (null == result || result == String.Empty)
   {
    result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
   }

   if (null == result || result == String.Empty)
   {
    result = HttpContext.Current.Request.UserHostAddress;
   }
   return result;
}

获取MAC地址:

[DllImport("Iphlpapi.dll")]
private static extern int SendARP(Int32 dest,Int32 host,ref Int64 mac,ref Int32 length);
[DllImport("Ws2_32.dll")]
private static extern Int32 inet_addr(string ip);

private void Page_Load(object sender, System.EventArgs e)
{
   // 在此处放置用户代码以初始化页面
   try
   {
    string userip=Request.UserHostAddress;
    string strClientIP = Request.UserHostAddress.ToString().Trim();
    Int32 ldest = inet_addr(strClientIP); //目的地的ip
    Int32 lhost = inet_addr("");   //本地服务器的ip
    Int64 macinfo = new Int64();
    Int32 len = 6;
    int res = SendARP(ldest,0, ref macinfo, ref len);
    string mac_src=macinfo.ToString("X");
    if(mac_src == "0")
    {
     if(userip=="127.0.0.1")
      Response.Write ("正在访问Localhost!");
     else
      Response.Write ("欢迎来自IP为" + userip + "的朋友！" + "<br>");
     return;
    }

    while(mac_src.Length<12)
    {
     mac_src = mac_src.Insert(0,"0");
    }

    string mac_dest="";

    for(int i=0;i<11;i++)
    {
     if (0 == (i % 2))
     {
      if ( i == 10 )
      {
       mac_dest = mac_dest.Insert(0,mac_src.Substring(i,2));
      }
      else
      {
       mac_dest ="-" + mac_dest.Insert(0,mac_src.Substring(i,2));
      }
     }
    }

    Response.Write ("欢迎来自IP为"+userip+ "<br>" + ",MAC地址为"+mac_dest+"的朋友！"

     +   "<br>");
   }
   catch(Exception err)
   {
    Response.Write(err.Message);
   }
}