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);
}
}