在FormClosing事件中关闭应用程序

Question

I am trying to close my application when closing the menu form. This is my code:

private void frmMenu_FormClosing(object sender, FormClosingEventArgs e)
{
    var result = MessageBox.Show("Do you want to close this application",
        "Alert", MessageBoxButtons.YesNo, MessageBoxIcon.Warning);
    if (result == DialogResult.Yes)
    {
        //this.Close();
        Application.Exit();
        //e.Cancel = false;
    }
    else
    {
        e.Cancel = true;
    }
}

When closing this message appears twice.

Answer 1

You don't have to do the exit again, just let it pass:

private void frmMenu_FormClosing(object sender, FormClosingEventArgs e)
{
    var result = MessageBox.Show("Do you want to close this application?",
        "Alert", MessageBoxButtons.YesNo, MessageBoxIcon.Warning);
    if (result == DialogResult.No)
    {
        e.Cancel = true;
    }
}

Answer 2

You can override the OnFormClosing method:

protected override void OnFormClosing(FormClosingEventArgs e) {
        base.OnFormClosing(e);
        if (!e.Cancel) {
            if (MessageBox.Show("Do you want to close this application?", "Close Application", MessageBoxButtons.YesNo) != DialogResult.Yes) {
                e.Cancel = true;
            }
        }
    }

Or following Hans Passant 's advice in the comments on using a bool (eg IsDataValid ) in your class:

private void frmMenu_FormClosing(object sender, FormClosingEventArgs e)
{ 
   if (!IsDataValid)
   {
       if(DialogResult.Yes == MessageBox.Show(Do you want to close this application?",
        "Alert", MessageBoxButtons.YesNo, MessageBoxIcon.Question))
           this.Dispose(); //or Application.Exit();
       else
            e.Cancel = true;
   }
   else
       this.Dispose(); //or Application.Exit();
}

Answer 3

You get two messages because Application.Exit(); is closing frmMenu , whereas you are currently closing it => frmMenu is closed twice.

If frmMenu is the main form of your application, meaning you should having something like that in your Program.cs file:

static class Program {
    [STAThread]
    static void Main() {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new FrmMenu());
    }
}

... then the application will exit when closing frmMenu . As said by derape , you then don't have to call Application.Exit()

Answer 4

    private void frmMenu_FormClosing(object sender, FormClosingEventArgs e)
    {
        if (MessageBox.Show("Do you want to close this application", "Alert", MessageBoxButtons.YesNo, MessageBoxIcon.Warning) == DialogResult.No)
        {
            e.Cancel = true;
        }

    }