...
    clmn.DoubleClick   += new System.EventHandler (this.clmn_DoubleClick);
    clmn.KeyUp   += new KeyEventHandler (this.clmn_KeyUp);
 ....


   private void 
   clmn_DoubleClick (object sender, System.EventArgs e)
   {
       //MouseEventArgs me = (MouseEventArgs)e ;// ----------------------------------------
 
       Console.WriteLine("ut.ClmnWin.DoubleClick: {0}", e);
   }

   private void 
   clmn_KeyUp (object sender, KeyEventArgs e)
   {
         Console.WriteLine("ut.ClmnWin.KeyUp: keyCode {0}  {1} {2}", e.KeyCode, Keys.Enter, Keys.Return);
     if (e.KeyCode == Keys.Enter || e.KeyCode == Keys.Return) {
         Console.WriteLine("ut.ClmnWin.KeyUp: 1");
//       OnDoubleClick(new MouseEventArgs(MouseButtons.Left,  1 , 1 , 1 , 0 ));
         OnDoubleClick(new EventArgs());
     }
   }

 
public class ut_ListBox : ListBox {
   public void onDCLick (  EventArgs e)    {  OnDoubleClick (e);}  //  < -----------------------------------
 
   
 }

 public class ClmnWin: System.Windows.Forms.Form  {
   private     ut_ListBox clmn;             //< ----------------------------------------------
 

.....
   private void 
   clmn_KeyUp (object sender, KeyEventArgs e)
   {
//         Console.WriteLine("ut.ClmnWin.KeyUp: keyCode {0}  {1} {2}", e.KeyCode, Keys.Enter, Keys.Return);
     if (e.KeyCode == Keys.Enter || e.KeyCode == Keys.Return) {
         if(CNST._debug) 
           Console.WriteLine("ut.clmn.KeyUp: 1");
//         OnDoubleClick(new EventArgs());

         clmn.onDCLick(new EventArgs());     //< -----------------------------------------
 
     }
     else if (e.KeyCode == Keys.Escape) {
         if(CNST._debug) 
           Console.WriteLine("ut.clmn.KeyUp: esc");
         clmn.SelectedIndex = - 1 ;
         Close();
     }
   }

....
}