1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Text;
 5 
 6 using System.Runtime.InteropServices;//必须引用这个命名空间
 7 
 8 namespace NetWorkConn_Demo
 9 {
10     class Program
11     {
12         [DllImport("wininet.dll")]
13         private extern static bool InternetGetConnectedState(out int connectionDescription, int reservedValue);
14 
15         static void Main(string[] args)
16         {
17             int flag = 0;
18             var isConn = InternetGetConnectedState(out flag, 0);
19             if (isConn)
20             {
21                 Console.WriteLine("网络已连接！");
22             }
23             else
24             {
25                 Console.WriteLine("网络已断开！");
26             }
27             Console.ReadKey();
28         }
29     }
30 }