Keeping forms open after the main form is closed

[stumorgan]

There is probably an extremely simple answer to this question and I'm
just being foolish.

I have a main form (let's say FormMain) which opens other forms (let's
say Form1, Form2). How do I keep those created forms, Form1 and Form2,
from closing when I close FormMain? Right now what I'm doing is
threading them by wrapping the Show method and in that threaded wrapper
I have a while loop that just does Application.DoEvents() as long as
the form hasn't been closed.

private void ShowForm() // this is the threaded function
this.Show();
while(!closed)
{
Application.DoEvents();
}
}

and in the form's Closed event I set closed = true.

It works just fine, but I feel like it's probably inefficient and I
think there has to be a better (and probably simpler) way of doing it.
Any ideas? Feel free to mock me for my stupidity.

 

[Chris Dunaway]

You probably have your FormMain as your start up object. When you
close that form, it closes the app.

Try starting your app from a Sub Main and then call Application.Run
without any arguments. The caveat to this is that when you need to
exit the app, you need to call Application.ExitThread.

 

[stumorgan]

Yes I was reading about that on another forum. How am I supposed to
know when all of the forms have been closed and that I need to call
Application.ExitThread()?

Just spitballing here, but I could pass a reference to the main program
as a parameter when I create the forms, and then have them tell the
main program when they are closing. Main program keeps a counter on
the number of open forms and once it goes down to 0 calls
Application.ExitThread().

Does that make any sense or is there a better / simpler way of doing
it? As you can tell I'm trying to condition myself to program
efficiently... Help is much appreciated.

 

[Guest]

Hi stumorgan,
what Chris and yourself are saying is an efficient way to code, a simple
example of this could be:

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Threading;

namespace WindowsApplication5
{
namespace WindowsApplication5
{
static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
//Create main message pump
Application.Run(new Form1());
}
}
}

public class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
//Show other forms in seperate thread
Thread t = new Thread(new ThreadStart(ShowForms));
t.IsBackground = false;
t.Start();

//Close the main form - this will exit the main
//UI thread message pump, but we will have another one
this.Close();
}

/// <summary>
/// Keeps track of the number of open forms
/// </summary>
int _formCount = 0;

private void ShowForms()
{
Form f1 = new Form();
Form f2 = new Form();

//Add event handler to decrement count on close
f1.FormClosed += new FormClosedEventHandler(ChildFormClosed);
f2.FormClosed += new FormClosedEventHandler(ChildFormClosed);

//store how mant forms there are open
_formCount = 2;

//show both the forms
f1.Show();
f2.Show();

//Create a new message pump outside of the main
//UI thread message pump
Application.Run();
}

void ChildFormClosed(object sender, FormClosedEventArgs e)
{
_formCount--;

//if no open forms - kill message pump
if (_formCount == 0)
{
//Tell the current thread to exit it message pump
Application.ExitThread();
}
}


}
}


Mark Dawson
http://www.markdawson.org