取消函数/进程

Question

我目前有一个 ping IP 列表的应用程序。 用户单击一个按钮，它会持续 ping 所有 IPS 20 秒。 我想要做的是单击一个按钮来停止它。

我创建了一个名为“Process”的函数，它会在单击按钮时调用此进程。

我试图创建一个 bool 值和 while 循环，当它为 false 并让停止按钮将 bool 值更改为 true，但它似乎并没有停止任何事情，事实上我什至无法关闭窗口，直到ping 已完成。

我的代码如下。

private bool _stopLoop;

    private void btnPlay_Click(object sender, EventArgs e)
    {
        Process();
    }

private void Process()
{
    while (_stopLoop == false)
    {
        for (int i = 0; i < 20; i++)
        {
            foreach (DataGridViewRow dataGridView1Row in dataGridView1.Rows)
            {
                var count = 20;
                progressBar1.Value = i * progressBar1.Maximum / count;
                Application.DoEvents();
                var url = dataGridView1Row.Cells[1].Value.ToString();
                int timeout = 500;
                Ping ping = new Ping();

                PingReply pingreply = ping.Send(url, timeout);
                PingReply result = null;
                IPStatus status;

                result = pingreply;
                status = result.Status;

                if (status != IPStatus.Success)
                {
                    dataGridView1Row.Cells[0].Style.BackColor = Color.Red;
                    dataGridView1Row.Cells[0].Value = "Offline";
                }
                else
                {
                    dataGridView1Row.Cells[0].Style.BackColor = Color.Green;
                    dataGridView1Row.Cells[0].Value = "Online";
                }



            }
        }
    }
}

private void btnStop_Click(object sender, EventArgs e)
{
  _stopLoop = true;
}

Answer 1

我只针对为什么循环不会停止的直接问题。实现后台线程或任务或后台工作者是更好的解决方案，但不是问题:)

正如我的评论所说，你只打破了你的“无限”循环，这是最外层的循环。

运行在您的 IP 上的两个内部循环（ foreach (DataGridViewRow dataGridView1Row in dataGridView1.Rows){ [...] } 以及您的“执行 20 次”循环 for (int i = 0; i < 20; i++){ [...] } 如果您希望它停止，则需要中断。

这意味着您可以像这样更改它们：

while (_stopLoop == false)
{
    for (int i = 0; i < 20; i++)
    {   
        foreach (DataGridViewRow dataGridView1Row in dataGridView1.Rows)
        {
            if(_stopLoop)
                 return; // finish execution and jump out of all loops, or use break to jump into the for loop, but then you need to break out of it as well
             
            /* your ping logic */

        }
    }
}

Answer 2

如果您使用 async/await，您的 GUI 可以响应，并且您的请求可以同时并发：

private CancellationTokenSource pingCancellation;

private async void btnPlay_Click(object sender, EventArgs e)
{
    const int pingTimeout = 500;
    var pingDuration = TimeSpan.FromSeconds(20);

    btnPlay.Enabled = false;
    dataGridView1.ReadOnly = true;

    var entries =
        dataGridView1.Rows.Cast<DataGridViewRow>()
                          .Where(r => !r.IsNewRow)
                          .Select(row => new { Row = row, Hostname = row.Cells[1].Value.ToString(), Ping = new Ping() })
                          .ToList();


    pingCancellation = new CancellationTokenSource();
    pingCancellation.Token.Register(() => entries.ForEach(e => e.Ping.SendAsyncCancel()));

    btnStop.Enabled = true;

    pingCancellation.CancelAfter(pingDuration);
    var finishTime = DateTime.UtcNow.Add(pingDuration);
    try
    {
        while (!pingCancellation.IsCancellationRequested)
        {
            await Task.WhenAll(entries.Select(async e =>
            {
                var result = await e.Ping.SendPingAsync(e.Hostname, pingTimeout);

                if (result.Status != IPStatus.Success)
                {
                    e.Row.Cells[0].Style.BackColor = Color.Red;
                    e.Row.Cells[0].Value = "Offline";
                }
                else
                {
                    e.Row.Cells[0].Style.BackColor = Color.Green;
                    e.Row.Cells[0].Value = "Online";
                }
            }).Concat(new[] { Task.Delay(pingTimeout, pingCancellation.Token) /*Rate limiting*/ }));

            progressBar1.Value = (int)Math.Min(progressBar1.Maximum * (pingDuration - (finishTime - DateTime.UtcNow)).Ticks / pingDuration.Ticks, progressBar1.Maximum);
        }
    }
    catch (TaskCanceledException)
    {
    }

    btnStop.Enabled = false;
    pingCancellation.Dispose();
    pingCancellation = null;
    foreach (var entry in entries)
    {
        entry.Ping.Dispose();
    }
    progressBar1.Value = 0;
    dataGridView1.ReadOnly = false;
    btnPlay.Enabled = true;
}

private void btnStop_Click(object sender, EventArgs e)
{
    if (pingCancellation != null && !pingCancellation.IsCancellationRequested)
    {
        pingCancellation.Cancel();
    }
}