DialogResult result = MessageBox.Show("Сохранить введеные данные", "Сохранение", MessageBoxButtons.YesNo);
if(result == DialogResult.Yes){
   //yes
}
else if(result == DialogResult.No){
   //no
}

public void clickHandler(object sender, System.EventArgs e)  {...}

button1.Click += new EventHandler(clickHandler); 
button2.Click += new EventHandler(clickHandler); 
button3.Click += new EventHandler(clickHandler);

foreach (Control ctrl in myGroupBox.Controls)
{
      ctrl.Click += new EventHandler(clickHandler); 
}