How to prevent Closing and Disposing of a winform in the FormClosing event?

Question

This question may seem like a duplicate, but I just ran in to this issue while I was testing my program and I am kind of confused as to how you solve it.

I have a wi

Answer 1

e.Cancel = true prevents the window from closing - it stops the close event.

e.Cancel = false allows the "close event" to continue (resulting in the window closing and being disposed; assuming nothing else stops it).

It seems you want to do this:

method PPMain.PPMain_FormClosing(sender: System.Object; e: System.Windows.Forms.FormClosingEventArgs);
begin
      e.Cancel := true; 
      if MessageBox.Show('Are you sure you want to close the window?','PPMain',MessageBoxButtons.YesNo) = DialogResult.Yes then
      begin
            Hide; 
      end
end

e.Cancel := true; prevents the window from closing. The user is then prompted, if they say yes Hide; hides the window (without disposing). If the user clicks No, nothing happens.

It might be a good idea to detect what kind of close action is being performed. Using e.CloseReason so as not to prevent closing during OS shutdown or something along those lines.

Like this:

method PPMain.PPMain_FormClosing(sender: System.Object; e: System.Windows.Forms.FormClosingEventArgs);
begin
      if e.CloseReason = System.Windows.Forms.CloseReason.UserClosing then
      begin
           e.Cancel := true; 
           if MessageBox.Show('Are you sure you want to close the window?','PPMain',MessageBoxButtons.YesNo) = DialogResult.Yes then
           begin
                 Hide;
           end
      end
end