public static bool CheckForInternetConnection(int timeoutMs = 10000, string url = null)
{
    try
    {
        url ??= CultureInfo.InstalledUICulture switch
        {
            { Name: var n } when n.StartsWith("fa") => // Iran
                "http://www.aparat.com",
            { Name: var n } when n.StartsWith("zh") => // China
                "http://www.baidu.com",
            _ =>
                "http://www.gstatic.com/generate_204",
        };

        var request = (HttpWebRequest)WebRequest.Create(url);
        request.KeepAlive = false;
        request.Timeout = timeoutMs;
        using (var response = (HttpWebResponse)request.GetResponse())
            return true;
    }
    catch
    {
        return false;
    }
}

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

工作

而不是检查，只需执行操作(web请求，邮件，ftp等)，并为请求失败做好准备，即使检查成功，您也必须这样做。

考虑以下几点:

1 - check, and it is OK
2 - start to perform action 
3 - network goes down
4 - action fails
5 - lot of good your check did

如果网络坏了，你的动作就会像ping一样迅速失败。

1 - start to perform action
2 - if the net is down(or goes down) the action will fail

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);         
}

private bool ping()
{
    System.Net.NetworkInformation.Ping pingSender = new System.Net.NetworkInformation.Ping();
    System.Net.NetworkInformation.PingReply reply = pingSender.Send(address);
    if (reply.Status == System.Net.NetworkInformation.IPStatus.Success)
    {                
        return true;
    }
    else
    {                
        return false;
    }
}

bool bb = System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable();

if (bb == true)
    MessageBox.Show("Internet connections are available");
else
    MessageBox.Show("Internet connections are not available");