从 WPF/XBAP 应用程序检测网络连接？

Question

有什么方法可以确定 XBAP（托管在浏览器中的 WPF）应用程序是否具有网络连接性？如果没有，用 C# 和 .NET 编写的传统 Windows 客户端如何确定它是否具有连接性？

基本上，该用例是在通过 WiFi 连接到内部网的移动笔记本电脑上运行的 XBAP 应用程序。笔记本电脑将无法连接到 Internet。 WiFi 连接可能存在也可能不存在，具体取决于用户当时所处的位置。

Answer 1

GateWayIPAddressInformation 应该可以工作：http://msdn.microsoft.com/en-us/library/system.net.networkinformation.gatewayipaddressinformation(loband).aspx

如果您获得网关 IP 地址，并且可以 Ping (http://msdn.microsoft.com/en-us/library/system.net.networkinformation.ping(loband).aspx)，则您可能已连接。

Answer 2

在您的 InitializeComponent() 中执行此操作：

// Add EventHandler for NetworkAddressChanged event    
NetworkChange.NetworkAddressChanged += new NetworkAddressChangedEventHandler(AddressChangedCallback);

这是触发该事件时调用的方法：

internal void AddressChangedCallback(object sender, EventArgs e)
{
    // Check for NetworkConnectivity
    _isInternetConnectionActive = new NetworkConnectivity().IsInternetConnected; 
}

这是 NetworkConnectivity 类：

public class NetworkConnectivity
{
    private List<IPAddress> _ipAddresses = new List<IPAddress>();

    public NetworkConnectivity()
    {
        _ipAddresses = new List<IPAddress>();
    }

    #region Public Properties
    public int CountIPAddresses
    {
        get { return this.IPAddresses.Count; }
    }
    public List<IPAddress> IPAddresses
    {
        get
        {
            _ipAddresses.Clear();
            // Get a listing of all network adapters
            NetworkInterface[] adapters = NetworkInterface.GetAllNetworkInterfaces();
            foreach (NetworkInterface adapter in adapters)
            {
                IPInterfaceProperties adapterProperties = adapter.GetIPProperties();
                GatewayIPAddressInformationCollection addresses = adapterProperties.GatewayAddresses;
                // If this adapter has at least 1 IPAddress
                if (addresses.Count > 0)
                {
                    // Loop through all IP Addresses
                    foreach (GatewayIPAddressInformation address in addresses)
                    {
                        _ipAddresses.Add(address.Address);
                    }
                }
            } 
            return _ipAddresses;
        }
    }
    public bool IsInternetConnected
    {
        get
        {
            if (this.CountIPAddresses == 0)
            {
                return false;
            }
            else
            {
                //IPAddress[] ips = ResolveDNSAddress("google.com");
                //return PingIPAddressPool(ips);
                return PingIPAddress("72.14.204.104"); // Google IP
            }
        }
    }
    #endregion

    #region Public Methods
    public IPAddress[] ResolveDNSAddress(string UrlAddress)
    {
        IPHostEntry hostInfo = Dns.Resolve(UrlAddress);
        return hostInfo.AddressList;
    }
    public bool PingIPAddressPool(IPAddress[] ipAddresses)
    {
        foreach (IPAddress ip in ipAddresses)
        {
            if (PingIPAddress(ip.Address.ToString()))
            {
                return true;
            }
        }
        return false;
    }
    public bool PingIPAddress(string ip)
    {
        // Pinging
        IPAddress addr = IPAddress.Parse(ip);
        Ping pingSender = new Ping();
        PingOptions options = new PingOptions();

        // Use the default Ttl value which is 128,
        // but change the fragmentation behavior.
        options.DontFragment = true;

        // Create a buffer of 32 bytes of data to be transmitted.
        string data = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
        byte[] buffer = Encoding.ASCII.GetBytes(data);
        int timeout = 15; // seconds to wait for response
        int attempts = 2; // ping attempts
        for (int i = 0; i < attempts; i++)
        {
            PingReply reply = pingSender.Send(addr, timeout, buffer, options); 
            if (reply.Status == IPStatus.Success)
            { return true; }
        }
        return false;
    }
    #endregion

}