根据@ChaosPandion的回答，为了尽可能确保结果是正确的，你可以像其他人指出的那样，包括多个大网站。但是，这应该异步完成，以避免太长的等待时间。此外，WebRequest、HttpWebRequest和HttpWebResponse类现在已经过时，应该被HttpClient取代。以下示例考虑了上述因素:

public static async Task<bool> CheckForInternetConnection(TimeSpan? timeoutMs = null, List<string> urls = null)
{
    if (timeoutMs == null)
    {
        timeoutMs = TimeSpan.FromSeconds(10);
    }

    var culture = CultureInfo.InstalledUICulture;
    if (urls == null)
    {
        urls = new List<string>();

        if (culture.Name.StartsWith("fa"))      // Iran
            urls.Add("http://www.aparat.com");
        else if (culture.Name.StartsWith("zh")) // China
            urls.Add("http://www.baidu.com");
        else
        {
            urls.Add("https://www.apple.com/");
            urls.Add("https://www.gstatic.com/generate_204");
        }
    }

    var client = new HttpClient();
    client.Timeout = (TimeSpan)timeoutMs;
    List<Task<string>> tasks = new List<Task<string>>();
    int unresponsiveUrlCount = 0;

    foreach (var url in urls)
    {   
        tasks.Add(client.GetStringAsync(url));             
    }

    Task aggregationTask = null;
    try
    {
        aggregationTask = Task.WhenAll(tasks);
        await aggregationTask;
    }
    catch (Exception)
    {  
        if (aggregationTask?.Exception?.InnerExceptions != null && aggregationTask.Exception.InnerExceptions.Any())
        {
            foreach (var innerEx in aggregationTask.Exception.InnerExceptions)
            {
                unresponsiveUrlCount++;
            }
        }      
    }

    return unresponsiveUrlCount < urls.Count;
}

该方法检查列表中的所有url，如果它们都不可访问，则返回false。我已经添加了苹果的url，因为在我的情况下，它加载相当快，但它可以替换为任何url。

尽量避免通过捕获异常来测试连接。因为我们真的预料到有时我们可能会失去网络连接。

 if (NetworkInterface.GetIsNetworkAvailable() &&
     new Ping().Send(new IPAddress(new byte[] { 8, 8, 8, 8 }),2000).Status == IPStatus.Success)
 //is online
 else
 //is offline

另一种选择是网络列表管理器API，它适用于Vista和Windows 7。MSDN文章在这里。在本文中有一个下载代码示例的链接，允许您这样做:

AppNetworkListUser nlmUser = new AppNetworkListUser();
Console.WriteLine("Is the machine connected to internet? " + nlmUser.NLM.IsConnectedToInternet.ToString());

请确保从COM选项卡中添加对网络列表1.0类型库的引用…它将显示为NETWORKLIST。

不能解决在检查和运行代码之间网络中断的问题吗 但是相当可靠

public static bool IsAvailableNetworkActive()
{
    // only recognizes changes related to Internet adapters
    if (System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable())
    {
        // however, this will include all adapters -- filter by opstatus and activity
        NetworkInterface[] interfaces = System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces();
        return (from face in interfaces
                where face.OperationalStatus == OperationalStatus.Up
                where (face.NetworkInterfaceType != NetworkInterfaceType.Tunnel) && (face.NetworkInterfaceType != NetworkInterfaceType.Loopback)
                select face.GetIPv4Statistics()).Any(statistics => (statistics.BytesReceived > 0) && (statistics.BytesSent > 0));
    }

    return false;
}

使用NetworkMonitor监控网络状态和internet连接。

示例:

namespace AmRoNetworkMonitor.Demo
{
    using System;

    internal class Program
    {
        private static void Main()
        {
            NetworkMonitor.StateChanged += NetworkMonitor_StateChanged;
            NetworkMonitor.StartMonitor();

            Console.WriteLine("Press any key to stop monitoring.");
            Console.ReadKey();
            NetworkMonitor.StopMonitor();

            Console.WriteLine("Press any key to close program.");
            Console.ReadKey();
        }

        private static void NetworkMonitor_StateChanged(object sender, StateChangeEventArgs e)
        {
            Console.WriteLine(e.IsAvailable ? "Is Available" : "Is Not Available");
        }
    }
}

我在我的3g路由器/调制解调器上的那些方法上有问题，因为如果互联网断开连接，路由器将页面重定向到它的响应页面，所以你仍然得到一个蒸汽，你的代码认为有互联网。 苹果(或其他)有一个热点删除页面，总是返回特定的响应。下面的示例返回“Success”响应。所以你会完全确定你可以连接互联网，并得到真实的回应!

public static bool CheckForInternetConnection()
{
    try
    {       
        using (var webClient = new WebClient())
        using (var stream = webClient.OpenRead("http://captive.apple.com/hotspot-detect.html"))
        {
            if (stream != null)
            {
                //return true;
                stream.ReadTimeout = 1000;
                using (var reader = new StreamReader(stream, Encoding.UTF8, false))
                {
                    string line;
                    while ((line = reader.ReadLine()) != null)
                    {
                        if (line == "<HTML><HEAD><TITLE>Success</TITLE></HEAD><BODY>Success</BODY></HTML>")
                        {
                            return true;
                        }
                        Console.WriteLine(line);
                    }
                }

            }
            return false;
        }
    }
    catch
    {

    }
    return false;
}