如何使用按钮停止长时间运行的循环

Question

I have c# application which having 2 buttons. First having for loop which is run 10k times. and each loop code execution take 1 second to finish.

    for(int i=0;i<10000;i++){
      //My running code take 1 sec for each loop
    }

some time i want to stop this loop/ execution on click on another button "Stop", but its not working. Please suggest me what solution.

Answer 1

It's not good practice to run long running operations in UI Thread (thread where all UI events are handled - such as button click). You should run your loop in another that.

You can use Task Parallel Library (TPL) :

    private bool stopIt = false;

    private void Form1_Load(object sender, EventArgs e)
    {
        Task task = Task.Factory.StartNew(() =>
            {
                for (int i = 0; i < 1000000000; i++)
                {
                    if (!stopIt)
                    {
                        Console.WriteLine("Here is " + i);
                    }
                    else
                    {
                        break;
                    }
                }
            });
    }

    private void button1_Click(object sender, EventArgs e)
    {
        stopIt = true;
    }

Answer 2

The simplest solution (not best) is to add Application.DoEvents() into the loop to process button events:

private bool cancel;

public void loop()
{
    for(int i=0;i<10000;i++){
      //My running code take 1 sec for each loop
       Application.DoEvents();
       if (cancel)
          break;
    }
}

public void cancelButton_Click(object sender, EventArgs e)
{
      cancel=true;
}

Much better and still simple solution is to employ async Task (the rest of the code stays the same minus Application.DoEvents() call):

private void loopButton_Click(object sender, EventArgs e)
{
    new Task(loop).Start();
}

Beware that you should use this.Invoke(new Action(() => { <your code> } )); to access UI controls from the loop in this case.