Closing window is occurring more than one time

private void Form2_FormClosing(object sender, FormClosingEventArgs e)
{
    DialogResult d = MessageBox.Show("Do u want to close application", "Exit", MessageBoxButtons.YesNo);
    if (d == DialogResult.Yes)
    {
        Application.Exit();
    }
    else if(d==DialogResult.No)
    {
        e.Cancel = true;
    }
}