Detect when a form has been closed c#

问题

I have a WinForm that I create that shows a prompt with a button. This is a custom WinForm view, as a message box dialog was not sufficient.

I have a background worker started and running. I also want to exit the while(aBackgroundWorker.IsBusy) loop if the button on myForm was clicked.

//MyProgram.cs

using(CustomForm myForm = new CustomForm())
{
    myForm.Show(theFormOwner);
    myForm.Refresh();

    while(aBackgroundWorker.IsBusy)
    {
        Thread.Sleep(1);
        Application.DoEvents();
    }
}

Right now, in the CustomForm the Button_clicked event, I have

//CustomForm.cs

private void theButton_Click(object sender, EventArgs e)
{
  this.Close();
}

Do I need to add more code to the CustomForm class, or the location where I declare and initialize the form in order to be able to detect a closure?

回答1:

To detect when the form is actually closed, you need to hook the FormClosed event:

    this.FormClosed += new FormClosedEventHandler(Form1_FormClosed);

    void Form1_FormClosed(object sender, FormClosedEventArgs e)
    {
        // Do something
    }

Alternatively:

using(CustomForm myForm = new CustomForm())
{
    myForm.FormClosed += new FormClosedEventHandler(MyForm_FormClosed);
    ...
}

void MyForm_FormClosed(object sender, FormClosedEventArgs e)
{
    // Do something
}

回答2:

You might be going overkill. To show a form like a dialog window and wait for it to exit before returning control back to the calling form, just use:

mySubForm.ShowDialog();

This will "block" the main form until the child is closed.

回答3:

Handle the FormClosing event of the form to be notified when the form is closing, so you can perform any cleanup.

回答4:

You should be able to hook into the FormClosing and FormClosed events.

http://msdn.microsoft.com/en-us/library/system.windows.forms.form.formclosing.aspx http://msdn.microsoft.com/en-us/library/system.windows.forms.form.formclosed.aspx

Closing is before it's closed. Closed is after it's closed.

回答5:

A couple things...

First, it appears that loop is there in order to prevent execution form proceeding while the dialog is open. If that is the case, change you .Show(parent) to .ShowDialog(parent). That will also take care of the rest of your question.

回答6:

Make sure your background worker supports cancellation and as others have pointed out use the form closed event handler. This code should point you in the right direction:

using(CustomForm myForm = new CustomForm())
{
  myForm.FormClosed += new FormClosedEventHandler(ChildFormClosed);
  myForm.Show(theFormOwner);
  myForm.Refresh();


  while(aBackgroundWorker.IsBusy)
  {
    Thread.Sleep(1);
    Application.DoEvents();
  }
}

void ChildFormClosed(object sender, FormClosedEventArgs e)
{
    aBackgroundWorker.CancelAsync();
}

回答7:

Note that this.Hide(); is not the same as this.Close(); in the actual dialog your overriding the closed event

来源：https://stackoverflow.com/questions/8750602/detect-when-a-form-has-been-closed-c-sharp

标签

winforms

events

event-handling