Cancel Close Problem

Okay my problem is this I want stop the user from closing the child form of my problem if there is only one open, but if I set the cancel event to true in the onclosing event it will not allow me to close the program. My first thought was the set a boolean value to check to see if the parent for was being closed but it did not work either. So basically im stumped at the moment.

Try a search using: single program instance mutex synchronization object. Read over a
few of the C# hits you get for this and then go steal and seriously study the code by
Michael Potter at: http://www.codeproject.com/csharp/cssingprocess.asp

One of the reasons you may want to limit the number of your parent form instances will
be so you can use runtime InteropServices to communicate between your multiples of forms.
I'm not saying you must limit your parent form; in fact, it could be a kewl study to do
it without any limit; but that's another story...

Once (assuming) you grasp how this is done with the above technique, it will hopefully
not be too big a leap to see how you can move from checking for a single instance in
Main() with RaiseOtherProcess to doing it when each of your forms are closing with:

Code:

---

public class frmMyBigForm : System.Windows.Forms.Form
{
.
.
.
  private void frmMyBigForm_Closing( object sender, System.ComponentModel.CancelEventArgs e )
  {
    try
    {       
    // if(MessageBox.Show("Do you stop this?", "My Brian Hurts", MessageBoxButtons.YesNo) == DialogResult.Yes)
    // e.Cancel = true;  // Cancel form closing event
      using(SingleProgramInstance spi = new SingleProgramInstance("WackOnTheHeadMakesLightsInTheSky"))
      {
        spi.RaiseAlternateOzzieProcess();
      }
    }
    catch ( Exception error )
    { 
      Console.WriteLine( "frmMyBigForm_Closing Error: " + error.Message );
    }
  }

---

FWIW, this should give you a serious lead into how to answer your form on top question too. ;) HTH.

geez that looks like a bit much for something so small ;\

in your main mdiform ( ie: the Parent ) ...

VB Code:

[Color=Blue]public[/color] [Color=Blue]bool[/color] ClosingForm=[Color=Blue]false[/color];
       [Color=Blue]protected[/color] [Color=Blue]override[/color] [Color=Blue]void[/color] WndProc([Color=Blue]ref[/color] Message m)
       {
       [Color=Blue]switch[/color](m.Msg)
       {
           [Color=Blue]case[/color] 161 :[Color=green] /// click on control box.[/color]
       [Color=Blue]if[/color](m.WParam.ToInt32()==20)[Color=green]/// click on close X[/color]
        {
             ClosingForm=[Color=Blue]true[/color];
        }
        [Color=Blue]break[/color];
        }
        [Color=Blue]base[/color].WndProc([Color=Blue]ref[/color] m);
        }

in your mdiChild's closing event ....

VB Code:

[Color=Blue]private[/color] [Color=Blue]void[/color] Form2_Closing([Color=Blue]object[/color] sender, System.ComponentModel.CancelEventArgs e)
        {
             Form1 fMain=(Form1)[Color=Blue]this[/color].MdiParent;
            [Color=Blue]if[/color]([Color=Blue]this[/color].MdiParent.MdiChildren.Length==1)
            {
                [Color=Blue]switch[/color](fMain.ClosingForm)
                {
                    [Color=Blue]case[/color] [Color=Blue]false[/color] :
                       e.Cancel=[Color=Blue]true[/color];
                        [Color=Blue]break[/color];
                    [Color=Blue]case[/color] [Color=Blue]true[/color] :
                        e.Cancel=[Color=Blue]false[/color];
                        [Color=Blue]break[/color];
                }
            }
        }

hope it helps :)

hey stranger, lol.

Thanks, one question tho does this work if the user clicks the icon in the left of the application and clicks close??? Sorry I cant test this atm Im at work

hi dude :D , that catches the windows messages for clicking on the toolbox , then on the close button X only , but if you catch the messages ( Console.WriteLine ( m.Msg.ToString()) ; ) etc... then you should be able to get any of the extra numerics you want for the events like click on icon area.
btw, hows life treating you without msn to terrorize? ;)

I never left I'm still there and kicking, I've been on msn for years and will be for many more. ;)

* ps. Check ur PMs on the board I have another question