芮源:
 public class IsInternet
    {
        /// <summary>
        /// 判断是否有网
        /// </summary>
        /// <returns>true为有网，false为无网</returns>
        public bool IsInternetAvailable()
        {
            try
            {
                Dns.GetHostEntry("www.google.com"); //using System.Net;
                return true;
            }
            catch (SocketException ex)
            {
                return false;
            }
        }
    }

芮源:
 IsInternet ty = new IsInternet();

芮源:
 if (ty.IsInternetAvailable()) return;

c# 判断是否有网