C# WinForms ShowDialog() call arbitrary method

Question

I'm working on a console application that creates a form to alert users of some given state - at a later stage, the code base will become a class library.

For now, however, I need to show the form (ShowDialog would be the best method here, I guess) THEN call an arbitrary method before the form closes.

As an example, I need to show the form, set the text value of a label control, wait for n number of seconds, then change the value of the label, then close the form. I know that this sounds a little trivial, but I'm trying to proof-of-concept the design.

I've taken a look around and it doesn't look like this is possible, as ShowDialog() requires me to close the form before I can continue through code listing in the calling method/class.

Here's what I have so far:

PopUpForm myForm = new PopUpForm(string messageToDisplay);
myForm.ShowDialog();
//call myForm.someMethod() here, before the form closes
//dispose of the form, now that we've no use for it
myform.Dispose();

//target method in PopUpform class
public void someMethod()
{
  lblText.Text = "Waiting for some reason";
  //wait n number of seconds
  lblText.Text = "Finished waiting. Form will now close";
  //it doesn't matter if the form closes before the user can see this.
}

It looks like ShowDialog() doesn't support this sort of behaviour. I'm looking into BackgroundWorker threads, but was wondering if anyone has any advice on this, or have encountered this before.

Answer 1

If you want to show the form, then continue working, then close it - you can do so via Form.Show() instead of Form.ShowDialog():

using (var myForm = new PopUpForm(messageToDisplay))
{
    myForm.Show(); // Show the form

    DoWork(); // Do your work...

    myForm.Close(); // Close it when you're done...
} 

However, if this is purely a console application (and doesn't have a message pump), then this will likely not work properly.

Other options would be to provide a timer within your Form to have it close, or pass a delegate into the Form to run your method on Show, after which it could close itself.

at a later stage, the code base will become a class library.

When you do this, you'll likely want to come up with a different mechanism to provide notifications. Coupling your library to a specific UI technology is a bad idea. It would likely be better to have your library just provide events or other notification, and allow the user to provide the UI/notification to the user.