轉：Check Your Internet Connection With C#

方法一：

How to check if your computer is connected to the internet with C#. It's much more easier that other tutorials I've seen in other sites. In deed, we're going to use a simple API function InternetGetConnectedState, to return a boolean variable.

This function takes two arguments :

The first one is an integer used with out keyword, that means that after calling the function, the variable will contain an interger that describes the connection state ( use of a modem, use of a proxy, offline mode...). Note that you must refer to www.msdn.com for more information about that.
The second one is a reserved variable that must be set to 0.

In this tutorial, we'll create a class with a static function that returns true if connected and false if not, using our API function in private state.

Check this out :

using System ; using System.Runtime ; using System.Runtime.InteropServices ; public class InternetCS { //Creating the extern function... [DllImport("wininet.dll")] private extern static bool InternetGetConnectedState( int out Description, int ReservedValue ) ; //Creating a function that uses the API function... public static bool IsConnectedToInternet( ) { int Desc ; return InternetGetConnectedState( out Desc, 0 ) ; } }

方法二：Net2.0新增類庫（System.Net.NetworkInformation）
#region 方法二
        /// <summary>
        /// 用於檢查IP地址或網域名稱是否可以使用TCP/IP協議訪問(使用Ping命令),true表示Ping成功,false表示Ping失敗
        /// </summary>
        /// <param name="strIpOrDName">輸入參數,表示IP地址或網域名稱</param>
        /// <returns></returns>
        public static bool PingIpOrDomainName(string strIpOrDName)
        {
            try
            {
                Ping objPingSender = new Ping();
                PingOptions objPinOptions = new PingOptions();
                objPinOptions.DontFragment = true;
                string data = "";
                byte[] buffer = Encoding.UTF8.GetBytes(data);
                int intTimeout = 120;
                PingReply objPinReply = objPingSender.Send(strIpOrDName, intTimeout, buffer, objPinOptions);
                string strInfo = objPinReply.Status.ToString();
                if (strInfo == "Success")
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }
            catch (Exception)
            {
                return false;
            }
        }
        #endregion