how to pause the function until button is clicked

Question

How to use Thread / BackgroundWorker / Timer / AutoResetEvent or something else to force function f to wait / suspend / pause until the button is clicked by user.

public Form1()
{
    InitializeComponent();
    if(f())
        MessageBox.Show("returned");
}

bool b=false;

private void button1_Click(object sender, EventArgs e)
{
    //do something
    b=true;
}

bool f()
{
    //what to put here

    //should be here only after b==true
    return true;
}

I could compare it should work like Console.ReadKey pauses the function until gets the input.

Why not showing the message or doing whatever you want on button click? — Igor Popov, Jun 05 '15 at 11:13
You have it backwards. Trigger the function _when_ the button is pushed. — John Saunders, Jun 05 '15 at 11:13
What John said. Events work just fine for code like this. Also, do not put code like this in the constructor. Try `Form.Load` instead, for example. And for more complex cases, `await` can be pretty powerful - but it shouldn't really be necessary most of the time. — Luaan, Jun 05 '15 at 11:18
possible duplicate of [Pause/Resume loop in Background worker](http://stackoverflow.com/questions/8359058/pause-resume-loop-in-background-worker) — Dmitry, Jun 05 '15 at 11:26
the point is not I want to always show message. It's just control point. The reason why i need to pause f function is waiting for WebClient.DownloadFile() function or canceling it by clicking the button1 — gangus, Jun 05 '15 at 14:11
@user3599362 - And that's the crucial piece of information that you should have included in your question at the start. — Enigmativity, Jun 05 '15 at 22:21

score 1 · Answer 1 · answered Jun 05 '15 at 19:40

As long as all you need is to cancel downloading using WebClient when button is clicked you can just use asynchronous downloading:

private WebClient _webClient;

public Form1()
{
    InitializeComponent();
    _webClient = new WebClient();
    _webClient.DownloadFileCompleted += (s, e) =>
      {
        try
        {
           if (e.Cancelled) 
             return;

           //do something with your file
        }
        finally
        {
          _webClient.Dispose(); 
        }
      };
    _webClient.DownloadFileAsync(...);
}

private void button1_Click(object sender, EventArgs e)
{
    _webClient.CancelAsync();
}

score 0 · Answer 2 · answered Jun 06 '15 at 09:39

0

I just managed this way:
I created background worker which lets to click button during executing download function.
f function waits until download function is finished (or interrupted).

answered Jun 06 '15 at 09:39

gangus

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1
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how to pause the function until button is clicked

2 Answers2