C#获取本机公网IP

/// <summary>
/// 获取本机公网IP
/// </summary>
/// <returns></returns>
public static string GetIP_Lan()
{
    string tempip = "127.0.0.1";
    try
    {
        WebRequest wr = WebRequest.Create("http://www.ip138.com/ip2city.asp");
        Stream s = wr.GetResponse().GetResponseStream();
        StreamReader sr = new StreamReader(s, Encoding.Default);
        string all = sr.ReadToEnd(); 
        int start = all.IndexOf("[") + 1;
        int end = all.IndexOf("]", start);
        tempip = all.Substring(start, end - start);
        sr.Close();
        s.Close();
    }
    catch
    {
    }
    return tempip;
}