NetworkInterface。GetIsNetworkAvailable非常不可靠。只是有一些VMware或其他局域网连接，它将返回错误的结果。 还有Dns。我只是关心测试URL是否可能在我的应用程序部署的环境中被阻止。

我发现的另一种方法是使用InternetGetConnectedState方法。 我的代码是

[System.Runtime.InteropServices.DllImport("wininet.dll")]
private extern static bool InternetGetConnectedState(out int Description, int ReservedValue);

public static bool CheckNet()
{
     int desc;
     return InternetGetConnectedState(out desc, 0);         
}

public static bool HasConnection()
{
    try
    {
        System.Net.IPHostEntry i = System.Net.Dns.GetHostEntry("www.google.com");
        return true;
    }
    catch
    {
        return false;
    }
}

工作

ping google.com会引入一个DNS解析依赖。ping 8.8.8.8很好，但谷歌离我很远。我所需要做的就是在互联网上ping离我最近的东西。

我可以使用Ping的TTL功能来Ping跳#1，然后跳#2，等等，直到我从一个可路由地址上的某个东西得到回复;如果该节点在一个可路由地址上，那么它就在因特网上。对于我们大多数人来说，跳点1将是我们的本地网关/路由器，跳点2将是光纤连接或其他设备的另一侧的第一个点。

这段代码对我有用，比这个线程中的其他一些建议反应更快，因为它是在互联网上ping离我最近的任何东西。

using System.Diagnostics;
using System.Net;
using System.Net.NetworkInformation;
using System.Net.Sockets;
using System.Threading.Tasks;
    
public static async Task<bool> IsConnectedToInternetAsync()
{
    const int maxHops = 30;
    const string someFarAwayIpAddress = "8.8.8.8";
    
    // Keep pinging further along the line from here to google 
    // until we find a response that is from a routable address
    for (int ttl = 1; ttl <= maxHops; ttl++)
    {
        var options = new PingOptions(ttl, true);
        byte[] buffer = new byte[32];
        PingReply reply;
        try
        {
            using (var pinger = new Ping())
            {
                reply = await pinger.SendPingAsync(someFarAwayIpAddress, 10000, buffer, options);
            }
        }
        catch (PingException pingex)
        {
            Debug.Print($"Ping exception (probably due to no network connection or recent change in network conditions), hence not connected to internet. Message: {pingex.Message}");
            return false;
        }
    
        string address = reply.Address?.ToString() ?? null;
        Debug.Print($"Hop #{ttl} is {address}, {reply.Status}");
    
        if (reply.Status != IPStatus.TtlExpired && reply.Status != IPStatus.Success)
        {
            Debug.Print($"Hop #{ttl} is {reply.Status}, hence we are not connected.");
            return false;
        }
    
        if (IsRoutableAddress(reply.Address))
        {
            Debug.Print("That's routable, so we must be connected to the internet.");
            return true;
        }
    }
    
    return false;
}
    
private static bool IsRoutableAddress(IPAddress addr)
{
    if (addr == null)
    {
        return false;
    }
    else if (addr.AddressFamily == AddressFamily.InterNetworkV6)
    {
        return !addr.IsIPv6LinkLocal && !addr.IsIPv6SiteLocal;
    }
    else // IPv4
    {
        byte[] bytes = addr.GetAddressBytes();
        if (bytes[0] == 10)
        {   // Class A network
            return false;
        }
        else if (bytes[0] == 172 && bytes[1] >= 16 && bytes[1] <= 31)
        {   // Class B network
            return false;
        }
        else if (bytes[0] == 192 && bytes[1] == 168)
        {   // Class C network
            return false;
        }
        else
        {   // None of the above, so must be routable
            return true;
        }
    }
}

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;
}

如果你想在网络/连接发生变化时通知用户/采取行动。 使用NLM API:

https://msdn.microsoft.com/en-us/library/ee264321.aspx http://www.codeproject.com/Articles/34650/How-to-use-the-Windows-NLM-API-to-get-notified-of

我有三个网络连接测试。

参考系统。Net和system.net.socket 增加以下测试功能:

测试1

public bool IsOnlineTest1()
{
    try
    {
        IPHostEntry dummy = Dns.GetHostEntry("https://www.google.com");
        return true;
    }
    catch (SocketException ex)
    {
        return false;
    }
}

测试2

public bool IsOnlineTest2()
{
    try
    {
        IPHostEntry dummy = Dns.GetHostEntry("https://www.google.com");
        return true;
    }
    catch (SocketException ex)
    {
        return false;
    }
}

测试3

public bool IsOnlineTest3()
{
    System.Net.WebRequest req = System.Net.WebRequest.Create("https://www.google.com");
    System.Net.WebResponse resp = default(System.Net.WebResponse);
    try
    {
        resp = req.GetResponse();
        resp.Close();
        req = null;
        return true;
    }
    catch (Exception ex)
    {
        req = null;
        return false;
    }
}

执行测试

如果您创建了一个名为CheckList的字符串和布尔字典，则可以将每个测试的结果添加到CheckList中。

现在，递归遍历每个KeyValuePair使用for…每一个循环。

如果检查表的值为true，则您知道有Internet连接。