c# Windows Forms: Form Close Event Cancel Button

Question

I have a Form_Closing event that prompts the user if the file has been changed to save if changes have been made to the file (standard Yes/No/Cancel options). Cancel is where things don't work as they should.

If I select File -> New and there is an existing file with changes I get prompted as expected, bit when I select Cancel the new form is presented rather than staying on the current form and I end up with two forms open at once.

Here is MainForm (File New) code:

       if (editForm != null)
        {
            // Close existing Editor form
            editForm.Close();
            // Open new form
            editForm = new EditorForm(this);
            // Close Form Events
            editForm.Closing += new CancelEventHandler(EditorForm_Closing);
            editForm.Show();
            editForm.Focus();

      else
        {
            // Open new Editor 
            editForm = new EditorForm(this);
            // Close Form Events
            editForm.Closing += new CancelEventHandler(EditorForm_Closing);
            editForm.Show();
            editForm.Focus();
        }

Here is my EditForm_Closing:

  if (editForm != null)
        {
            if (editForm.diagramComponent.Model.Modified)
            {
                DialogResult res = MessageBox.Show(this, "The project has been modified. Save changes?", "Save changes", MessageBoxButtons.YesNoCancel);
                if (res == DialogResult.Yes)
                {
                    if (!editForm.HasFileName)
                    {
                        if (this.saveEditorDialog1.ShowDialog(this) == DialogResult.OK)
                        {
                            this.ActiveDiagram.SaveSoap(this.saveEditorDialog1.FileName);
                            editForm.FileName = this.saveEditorDialog1.FileName;
                        }
                    }
                    else
                    {
                        this.ActiveDiagram.SaveSoap(editForm.FileName);
                    }

                }
                else if (res == DialogResult.Cancel)
                {
                    e.Cancel = true;
                }
            }

Not sure how to make the correlation between the Cancel close event and my File -> New. Any help is greatly appreciated. Thank you.

EDIT: Added my EditForm_Closing Event.

Solution 1

Try replacing your main form's code with the following:

if (editForm != null) {
    // try closing existing Editor form
    editForm.Close();
    if(!editForm.IsDisposed) // close was canceled.
        return;
}

// Open new form
editForm = new EditorForm(this);
// Close Form Events
editForm.FormClosing += new FormClosingEventHandler('suitable method here');
editForm.Show();
editForm.Focus();

Solution 2

Your Closing event handler should set the editForm property back to null. So check it like this:

if (editForm != null) {
    editForm.Close();
    if (editForm != null) return;  // Close was cancelled
    // etc..
}

Or just use a private boolean member.

Comments

[jonalodev]

ahhh, i added return; to my DialogResult.Cancel and that seemed to work when i try to just close the form thank you! however, when i click file -> new it still opens a second window.

[user1703401]

Are you setting the editForm field to null in the Closing event handler? Important, you don't want to leak the instance.

[Sergei Z]

I cannot test whether it works, and if it does, make sure you disconnect the FormClosingEventHandler appropriately in the handler as well (if you're not canceling, that is, allowing the editor to close).