C# 检测当前网络状态（能否上网）

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Net.NetworkInformation;
using System.Net.Sockets;
using System.Net;
using System.Runtime.InteropServices;
namespace Ex15_04
{
    public partial class Form1 : Form
    {
        public Form1（）
        {
            InitializeComponent（）;
        }
        [DllImport（“wininet.dll“ EntryPoint = “InternetGetConnectedState“）]
        public extern static bool InternetGetConnectedState（out int conState int reder）;
        //参数说明 constate 连接说明 ，reder保留值
        public bool IsConnectedToInternet（）
        {
            int Desc=0;
            return InternetGetConnectedState（out  Desc 0）;
    

 属性            大小     日期    时间   名称
----------- ---------  ---------- -----  ----
     目录           0  2010-04-06 13:10  Ex15_04\
     文件         910  2007-07-11 11:34  Ex15_04.sln
     文件       28672  2007-07-11 11:34  Ex15_04.suo
     目录           0  2010-04-06 13:10  Ex15_04\bin\
     目录           0  2010-04-06 13:10  Ex15_04\bin\Debug\
     文件       24576  2007-07-11 11:34  Ex15_04\bin\Debug\Ex15_04.exe
     文件       24064  2007-07-11 11:34  Ex15_04\bin\Debug\Ex15_04.pdb
     文件        5658  2007-07-11 11:34  Ex15_04\bin\Debug\Ex15_04.vshost.exe
     文件        3329  2007-07-11 11:34  Ex15_04\Ex15_04.csproj
     文件        1314  2007-07-11 11:34  Ex15_04\Form1.cs
     文件        3887  2007-07-11 11:34  Ex15_04\Form1.Designer.cs
     文件        5814  2007-07-11 11:34  Ex15_04\Form1.resx
     目录           0  2010-04-06 13:10  Ex15_04\obj\
     目录           0  2010-04-06 13:10  Ex15_04\obj\Debug\
     文件         877  2007-07-11 11:34  Ex15_04\obj\Debug\Ex15_04.csproj.GenerateResource.Cache
     文件       24576  2007-07-11 11:34  Ex15_04\obj\Debug\Ex15_04.exe
     文件         180  2007-07-11 11:34  Ex15_04\obj\Debug\Ex15_04.Form1.resources
     文件       24064  2007-07-11 11:34  Ex15_04\obj\Debug\Ex15_04.pdb
     文件        4612  2007-07-11 11:34  Ex15_04\obj\Debug\Ex15_04.Properties.Resources.resources
     目录           0  2010-04-06 13:10  Ex15_04\obj\Debug\TempPE\
     文件        4608  2007-07-11 11:34  Ex15_04\obj\Debug\TempPE\Properties.Resources.Designer.cs.dll
     文件         268  2007-07-11 11:34  Ex15_04\obj\Ex15_04.csproj.FileList.txt
     文件         466  2007-07-11 11:34  Ex15_04\Program.cs
     目录           0  2010-04-06 13:10  Ex15_04\Properties\
     文件        1162  2007-07-11 11:34  Ex15_04\Properties\AssemblyInfo.cs
     文件        3078  2007-07-11 11:34  Ex15_04\Properties\Resources.Designer.cs
     文件        6189  2007-07-11 11:34  Ex15_04\Properties\Resources.resx
     文件        1090  2007-07-11 11:34  Ex15_04\Properties\Settings.Designer.cs
     文件         249  2007-07-11 11:34  Ex15_04\Properties\Settings.settings
     目录           0  2010-04-06 13:10  Ex15_04\Resources\
     文件        4150  2007-07-11 11:34  Ex15_04\Resources\1.bmp
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