Question

我有一项耗时的任务，可以测试几个网络连接。在我下面的例子中，我将它限制在一个连接中。通常，连接会快速返回，但可能会发生无法建立连接以致套接字超时的情况。在这段时间我想在表单中显示一个“闲人”gif，当连接成功时应用程序应该将表单中的图像更改为某些绿色检查图标或如果连接失败，应显示红色图标“塞子”。

不知怎的，我无法让闲人的GIF变得可见和动画。要模拟失败的连接，可以输入无效的端口＃或不存在的地址。

有什么线索我错过了什么或做错了什么？

    partial class Form1
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        ///         
     #region BackgroundWorker

        private System.ComponentModel.BackgroundWorker backgroundWorker = new System.ComponentModel.BackgroundWorker();
        private delegate void SomeLongRunningMethodHandler(object sender, EventArgs e);

     #endregion
        private System.ComponentModel.IContainer components = null;

        Button button,button2;
        static Socket socket;
        static bool success;
        private static bool done;
        private Label lbl1;
        private Label lbl2;
        private TextBox address;
        private TextBox port;
        private PictureBox p;
        private static String port_number,host;


        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        private void RunTest(object o,EventArgs e)
        {
            p.Visible = true;
            SomeLongRunningMethodHandler synchronousFunctionHandler =
                default(SomeLongRunningMethodHandler);
            synchronousFunctionHandler = 
                TestConnection;
            synchronousFunctionHandler.Invoke(o, e);
        }

        private void TestConnection(object o, EventArgs e)
        {
            host = address.Text;
            port_number = port.Text;
           if (null != socket)
            {
                socket.Close();
            }

             Thread.Sleep(1000);
             IPEndPoint myEndpoint = new IPEndPoint(0, 0);


            IPHostEntry remoteMachineInfo = Dns.GetHostEntry(host);
            IPEndPoint serverEndpoint = new IPEndPoint(remoteMachineInfo.AddressList[0],
                int.Parse(port_number));



            socket = new Socket(myEndpoint.Address.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
            try
            {
                socket.Connect(serverEndpoint);
                success = true;
                p.Image = global::BlockingUI.Properties.Resources.accept;
            }
            catch
            {
                success = false;
                p.Image = global::BlockingUI.Properties.Resources.stopper;
            }
            done = true;
        }  


        private void ExitApp(object o, EventArgs e)
        {
            Application.Exit();
        }

    }

Answer 1

如果你真的想使用BackgroundWorker，这个（或接近它的东西）应该指向正确的方向。您正在创建一个BackgroundWorker对象，但之后无法执行任何操作。不允许BackgroundWorker个对象访问UI元素，因为它们归UI线程所有，但您可以传入UI值，就像我在这里使用Tuple一样（您可以创建自己的类来保存）如果您也想要这些值，然后在工作完成后从UI线程修改UI。

private struct ConnectionProperties
{
    public string Address;
    public string Port;
}

private void RunTest(object o, EventArgs e)
{
    BackgroundWorker worker = new System.ComponentModel.BackgroundWorker();

    worker.RunWorkerCompleted += TestComplete;
    worker.DoWork += TestConnection;

    p.Visible = true;

    //worker.RunWorkerAsync(new Tuple<string, string>(address.Text, port.Text));
    worker.RunWorkerAsync(new ConnectionProperties{ Address = address.Text, Port = port.Text });
}

private void TestConnection(object sender, DoWorkEventArgs e)
{
    bool success = false;
    //var connection = e.Argument as Tuple<string, string>;
    var connection = (ConnectionProperties)e.Argument;

    if (null != socket)
    {
        socket.Close();
    }

    Thread.Sleep(1000);

    IPEndPoint myEndpoint = new IPEndPoint(0, 0);
    IPHostEntry remoteMachineInfo = Dns.GetHostEntry(connection.Address);
    IPEndPoint serverEndpoint = new IPEndPoint(remoteMachineInfo.AddressList[0],
      int.Parse(connection.Port));

    socket = new Socket(myEndpoint.Address.AddressFamily, SocketType.Stream, ProtocolType.Tcp);

    try
    {
        socket.Connect(serverEndpoint);
        success = true;
    }
    catch
    {
        success = false;
    }

    e.Result = success;
}

// Define other methods and classes here
private void TestComplete(object sender, RunWorkerCompletedEventArgs e)
{
    if (e.Error == null)
    {
        var success = (bool)e.Result;
        if (success)
        {
            p.Image = global::BlockingUI.Properties.Resources.accept;
        }
        else
        {
            p.Image = global::BlockingUI.Properties.Resources.stopper;
        }
    }
    else
    {
        //unexpected error, show message or whatever
    }
}

Answer 2

好吧，我用自己的线程完成了这个。通常，您使用长时间运行的任务运行线程，并在需要时调用Control.Invoke（），其中委托指向将在UI上运行的函数。看起来您正在使用后台工作线程更改UI，这是不允许的。

此外，在Winforms中需要调用Control.Invalidate（）来强制重新绘制UI并显示新图标。

在C＃Form应用程序中使用BackGroundWorker更新UI线程

2 个答案: