Question

I have a MDI form where some of the children forms need a message box showing before being closed and others could be closed without asking. Because of a problem when calling application.Exit() from a close event of a child form I handle to close event of the parent and check where it was fired. If it was fired in a form that need a message box I call it otherwise just close the application. All this is implemented in this code:

private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            SEdit se       = this.ActiveMdiChild as SEdit;
            SoEdit soleEdit = this.ActiveControl as SoEdit;
            UppEdit ue      = this.ActiveControl as UpEdit;
            MEdit mat  = this.ActiveControl as MEdit;
            LEdit lse      = this.ActiveControl as LEdit;
            CEdit cle    = this.ActiveControl as CEdit;

            if (se != null || soleEdit != null || ue != null || mat != null || lse != null || cle != null)
            {
                if (MessageBox.Show("Do you want to save before exit?", "Closing",
                      MessageBoxButtons.YesNo,
                      MessageBoxIcon.Information) == DialogResult.Yes)
                {
                    MessageBox.Show("To Do saved.", "Status",
                              MessageBoxButtons.OK,
                              MessageBoxIcon.Information);
                }
            }
         }

I’m still learning but I know that such a long if-statement is a sign for bad code but i don’t know how to improve it. What is the proper way to handle this situation?

Answer 1

Extract condition to separate method:

private bool AnyChildAlive()
{
   return (this.ActiveMdiChild is SEdit) ||
          (this.ActiveControl is SoEdit) ||
          ...
          (this.ActiveControl is CEdit);
}

Then call this method (also use guard conditions to avoid nested if statements):

private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
{          
    if (!AnyChildAlive())
       return;

    if (MessageBox.Show("Do you want to save before exit?", "Closing",
           MessageBoxButtons.YesNo, 
           MessageBoxIcon.Information) != DialogResult.Yes)
       return;

   MessageBox.Show("To Do saved.", "Status",
        MessageBoxButtons.OK, MessageBoxIcon.Information);     

}