Question

我花了几天时间在Google上搜索并试图理解为什么在我执行任务中执行ping时，Windows Forms 用户界面被阻止。我看到了很多类似的案例，但没有一个案例能解释我的具体案例。

问题描述：

我有一个异步发送ping的应用程序。每个ping都在Task内部发送。我使用.ContinueWith来接收ping的结果并将其打印到文本框而不阻止UI线程。 如果我一次启动所有ping，它就可以正常工作。如果我添加while {run}循环使它们永远运行，我的UI就会变得无法响应并被阻止，并且没有任何结果会打印到文本框中。

有问题的代码：

Action action2 = () => {
        for (int i = 0; i < ipquantity; i++)
        {
            int temp1 = i;
            string ip = listView1.Items[temp1].SubItems[1].Text;

            if (finished[temp1] == true) // Variable helps to check if ping reply was received and printed
                continutask[temp1] = Task<string>.Run(() => PingStart(ip, temp1)).ContinueWith(antecedent => PrintResult(antecedent.Result, temp1));
        }
};

while (run)
{
    action2();
    Thread.Sleep(1000);
}

问题：

为什么UI被while循环阻止，为什么没有阻止它？
如何修改我的代码，以便仍然可以在不阻止UI的情况下将ping用于任务？
是否有更好的方法可以同时向多个IP地址发送无限次ping？

完整代码：

private async void buttonStart_Click(object sender, EventArgs e)
{
    run = true;

    int count = listView1.Items.Count;
    task = new Task<string>[count];
    result1 = new string[count];
    finished = new bool[count];
    continutask = new Task[count];
    for (int i = 0; i < count; i++)
    {
        finished[i] = true;
    }

        Action action2 = () =>
    {
        for (int i = 0; i < count; i++)
        {
            int temp1 = i;
            string ip = listView1.Items[temp1].SubItems[1].Text;


            if (finished[temp1] == true)
                continutask[temp1] = Task<string>.Run(() => PingStart(ip, temp1)).ContinueWith(antecedent => PrintResult(antecedent.Result, temp1));

        }
    };
    while (run)
    {
        action2();
        //await Task.Delay;
        //Thread.Sleep(1000);
    }
}

public void PrintResult(string message, int seqnum)
{
    Action action = () =>
    {
        textBox1.AppendText(message);
        textBox1.AppendText(Environment.NewLine);
        textBox1.AppendText("");
        textBox1.AppendText(Environment.NewLine);
    };
    if (InvokeRequired)
        Invoke(action);
    else
        action();
    finished[seqnum] = true;
}

public string PingStart(string ip, int seqnum)
{
    finished[seqnum] = false;

    Ping isPing = new Ping();
    PingReply reply;
    const int timeout = 2000;
    const string data = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
    var buffer = Encoding.ASCII.GetBytes(data);
    PingOptions options = new PingOptions();
    // Use the default Ttl value which is 128,
    options.DontFragment = false;

    reply = isPing.Send(ip, timeout, buffer, options);
    string rtt = (reply.RoundtripTime.ToString());

    string success = "N/A";

    if (reply.Status == IPStatus.Success)
    {
        success = $"{ip}" + " Success!" + $" rtt: [{rtt}]" + $"Thread: {Thread.CurrentThread.GetHashCode()} Is pool thread: {Thread.CurrentThread.IsThreadPoolThread}";
    }
    else if (reply.Status != IPStatus.Success)
    {
        success = $"{ip}" + $" Not Successful! Status: {reply.Status}" + $"Thread: {Thread.CurrentThread.GetHashCode()} Is pool thread: {Thread.CurrentThread.IsThreadPoolThread}";
    }

    return success;
}

Answer 1

由于您已经创建（并保存）了您的任务，因此最简单的修复方法是在while循环的每次迭代中等待它们：

while (run)
{
    action2();

    foreach (Task t in continutask)
        await t;
}

这样，当所有ping完成（成功或不成功）时，你会再次开始整个过程 - 没有延迟。

还有一件事：您可以向textBox1.ScrollToEnd();

添加PrintResult

由于存在很大的改进空间，下面是一个重写和简化的例子。我删除了很多未使用的变量（例如seqnum）并使PingStart方法完全异步。我还使用TextBox替换了ListBox以便于测试，因此您可能希望在代码中恢复它。

这仍然不是所有可能实现的最干净的（主要是因为全局run）但它应该向您展示如何做事“more async”< / em>：）

private async void buttonStart_Click(object sender, EventArgs e) { // If the ping loops are already running, don't start them again if (run) return; run = true; // Get all IPs (in my case from a TextBox instead of a ListBox string[] ips = txtIPs.Text.Split(new[] {"\r\n"}, StringSplitOptions.RemoveEmptyEntries); // Create an array to store all Tasks Task[] pingTasks = new Task[ips.Length]; // Loop through all IPs for(int i = 0; i < ips.Length; i++) { string ip = ips[i]; // Launch and store a task for each IP pingTasks[i] = Task.Run(async () => { // while run is true, ping over and over again while (run) { // Ping IP and wait for result (instead of storing it an a global array) var result = await PingStart(ip); // Print the result (here I removed seqnum) PrintResult(result.Item2); // This line is optional. // If you want to blast pings without delay, // you can remove it await Task.Delay(1000); } } ); } // Wait for all loops to end after setting run = false. // You could add a mechanism to call isPing.SendAsyncCancel() instead of waiting after setting run = false foreach (Task pingTask in pingTasks) await pingTask; } // (very) simplified explanation of changes: // async = this method is async (and therefore awaitable) // Task<> = This async method returns a result of type ... // Tuple<bool, string> = A generic combination of a bool and a string // (-)int seqnum = wasn't used so I removed it private async Task<Tuple<bool, string>> PingStart(string ip) { Ping isPing = new Ping(); const int timeout = 2000; const string data = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"; var buffer = Encoding.ASCII.GetBytes(data); PingOptions options = new PingOptions {DontFragment = false}; // await SendPingAsync = Ping and wait without blocking PingReply reply = await isPing.SendPingAsync(ip, timeout, buffer, options); string rtt = reply.RoundtripTime.ToString(); bool success = reply.Status == IPStatus.Success; string text; if (success) { text = $"{ip}" + " Success!" + $" rtt: [{rtt}]" + $"Thread: {Thread.CurrentThread.GetHashCode()} Is pool thread: {Thread.CurrentThread.IsThreadPoolThread}"; } else { text = $"{ip}" + $" Not Successful! Status: {reply.Status}" + $"Thread: {Thread.CurrentThread.GetHashCode()} Is pool thread: {Thread.CurrentThread.IsThreadPoolThread}"; } // return if the ping was successful and the status message return new Tuple<bool, string>(success, text); }

这样，每个IP都会有一个循环，它会相互独立地继续，直到run设置为false。

Answer 2

Thread.Sleep（n）阻止当前线程n毫秒。如果我正确理解代码，它会执行 action2 ，然后暂停调用线程一秒钟。如果该线程是主（UI）线程，则您的UI将被阻止。

也许将同时循环移动到另一个线程可以解决问题。

使用ContinueWith执行任务时为什么阻止Windows窗体UI？

问题描述：

问题：

完整代码：

2 个答案: