Question

我尝试实施（在 WPF ， C＃）Ellipse控件，根据与google.com的连接更改颜色。如果与 Google 有连接，则椭圆为绿色;否则它是红色的。

我用这种方式编码：

XAML代码

<Window.Resources>
    <l:InternetConnectionToBrushConverter x:Key="InternetConnectionConverter" />
</Window.Resources>
<Grid>
    <DockPanel LastChildFill="True">
        <StatusBar Height="23" Name="statusBar1" VerticalAlignment="Bottom" DockPanel.Dock="Bottom">
            <Label Content="Google connection:" Name="label1" FontSize="10" Padding="3" />
            <Ellipse Name="ellipse1" Stroke="Black" Width="10" Height="10" Fill="{Binding Converter={StaticResource InternetConnectionConverter}}" Margin="0,4,0,0" />
        </StatusBar>
    </DockPanel>
</Grid>

和C＃后置代码（值转换器和函数检查连接）：

public class InternetConnectionToBrushConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (targetType != typeof(Brush))
            throw new InvalidOperationException("The target must be a Brush!");

        return CheckConnection("http://www.google.com/") == true ? Brushes.Green : Brushes.Red;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }

    /// <summary>
    /// Checks connection to specified URL. 
    /// </summary>
    /// <param name="URL"></param>
    /// <returns><b>True</b> if there is connection. Else <b>false</b>.</returns>
    private bool CheckConnection(String URL)
    {
        try
        {
            HttpWebRequest request = WebRequest.Create(URL) as HttpWebRequest;
            request.Timeout = 15000;
            request.Credentials = CredentialCache.DefaultNetworkCredentials;
            HttpWebResponse response = request.GetResponse() as HttpWebResponse;

            return response.StatusCode == HttpStatusCode.OK ? true : false;
        }
        catch (Exception e)
        {
            Debug.WriteLine(e.ToString());
            return false;
        }
    }

}

它运作良好但存在两个问题：

检查连接需要一些时间，所以我认为我应该在新线程中进行（如果我错了，请告诉我原因）
更重要的是 - 当程序开始运行时，它只检查与Google的连接一次（尽管我使用绑定，所以我希望会有持续的连接监控）

我该如何解决这个问题？
我希望有持续的连接监控，这样当我断开互联网连接时，Ellipse控件将改变其颜色。

Answer 1

你必须稍微改变你的架构您无法在IValueConverter中使用线程来避免锁定UI。在从IValueConverter返回之前，您仍需要等待线程完成。

您需要创建一个HasConnection属性来将椭圆颜色绑定到。然后，您可以在另一个线程中运行连接检查。最好使用BackgroundWorker。检查完成后，应更新HasConnection属性。然后，您可以定期使用计时器并检查连接，并在每次检查后更新HasConnection。

修改
您还可以监视NetworkChange.NetworkAvailabilityChanged事件，以了解本地网络连接何时启动或关闭。但是，如果您希望确保实际连接到目标，则应保留旧的CheckConnection，但在网络可用性发生变化时定期在计时器上启动时调用CheckConnection。

Answer 2

使用后台工作程序在后台监视，使用ReportProgress获取当前状态

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    // Get the BackgroundWorker that raised this event.
    BackgroundWorker worker = sender as BackgroundWorker;

    bool connected = false;
    string url = "https://www.google.com/";

    while (!worker.CancellationPending)
    {
        try
        {
            HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
            request.Timeout = 15000;
            request.Credentials = CredentialCache.DefaultNetworkCredentials;
            HttpWebResponse response = request.GetResponse() as HttpWebResponse;

            connected = (response.StatusCode == HttpStatusCode.OK);
            backgroundWorker1.ReportProgress(10, connected);
            Thread.Sleep(1000);

        }
        catch (Exception ex)
        {
            System.Diagnostics.Debug.WriteLine(ex.ToString());
            e.Cancel = true;
            e.Result = "cancelled";

            //return false;
        }
    }
    e.Result = connected;
}

private void backgroundWorker1_ProgressChanged(object sender,
    ProgressChangedEventArgs e)
{
    this.tbResult.Text = e.ProgressPercentage.ToString();
    System.Diagnostics.Debug.WriteLine(e.UserState.ToString());
}

监控互联网连接的状态

2 个答案: