Show a form while BackgroundWorker is running

问题

I want to display a "loading form" (a form with some text message plus a progressBar with style set to marquee) while the BackgroundWorker's job isn't done. When the BackgroundWorker is done, the loading form must be closed automatically. Although I do use a BackgroundWorker, the main thread should wait until it's done. I was able to do that using a AutoResetEvent but I noticied that as it does block the main thread, the form loading's progressBar is freezed too.

My question is: How can I show that form without freeze it while runing a process in background and wait for it finish? I hope it's clear.

Here's my current code:

    BackgroundWorker bw = new BackgroundWorker();
    AutoResetEvent resetEvent = new AutoResetEvent(false);
    //a windows form with a progressBar and a label
    loadingOperation loadingForm = new loadingOperation(statusMsg);
    //that form has a progressBar that's freezed. I want to make 
    // it not freezed.
    loadingForm.Show();

    bw.DoWork += (sender, e) =>
    {
        try
        {
            if (!e.Cancel)
            {
               //do something
            }
        }
        finally
        {
            resetEvent.Set();
        }
    };

    bw.RunWorkerAsync();
    resetEvent.WaitOne();
    loadingForm.Close();
    MessageBox.Show("we are done!");

回答1:

Connect your BackgroundWorker's RunWorkerCompleted to a callback that will close the form like so:

private void backgroundWorker1_RunWorkerCompleted(
    object sender, RunWorkerCompletedEventArgs e)
{
    loadingForm.Close();  
    MessageBox.Show("we are done!");
}

You can delete the resetEvent.WaitOne();

You'll need to make loadingForm a field of course.

Tell me more

Occurs when the background operation has completed, has been canceled, or has raised an exception

BackgroundWorker.RunWorkerCompleted

回答2:

Make the login form object an instance variable.

//use RunWorkerCompleted event to get notified about work completion where you close the form.
bw.RunWorkerCompleted += bw_RunWorkerCompleted;

event handler code:

private void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    this.loadingForm.close();    
}

Reference: https://msdn.microsoft.com/en-us/library/system.componentmodel.backgroundworker.runworkercompleted(v=vs.110).aspx

回答3:

Cek this script, Loading is Form with PictureBox - image gif

private delegate void showProgressCallBack(int value);

private void btnStart5_Click(object sender, EventArgs e)
    {
        BackgroundWorker bw = new BackgroundWorker();
        Loading f = new Loading();
        f.Show();

        bw.DoWork += (s, ea) =>
        {
            try
            {
                test1();
            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.Message); 
            }
        };
        bw.RunWorkerCompleted += (s, ea) =>
        {
            f.Close();
        };

        bw.RunWorkerAsync();
    }

private void showProgress(int value)
    {
        if (progressBar1.InvokeRequired)
        {
            showProgressCallBack showProgressDelegate =  new showProgressCallBack(showProgress);
            this.Invoke(showProgressDelegate, new object[] {value});
        }
        else
        {
            progressBar1.Value = value;
        }
    }

private void test()
    {
        showProgress(20);
        Thread.Sleep(3000);
        showProgress(80);
        Thread.Sleep(2000);
        showProgress(100);
    }

来源：https://stackoverflow.com/questions/29382305/show-a-form-while-backgroundworker-is-running

标签

multithreading

winforms

backgroundworker