public static AgregarUser Instance()
 {
     if (((frmInstance == null) || (frmInstance.IsDisposed == true)))
     {
         frmInstance = new AgregarUser();
     }
     frmInstance.BringToFront();
     return frmInstance;
 }
 private void AGREGAR(object sender, EventArgs e)
 {
     AgregarUser user = new AgregarUser();
     user.ShowDialog();
 }