public static FrmAdelantoCarga Instance()
        {
            if (frmInstance == null || frmInstance.IsDisposed == true)
            {
                frmInstance = new FrmAdelantoCarga();
            }

            frmInstance.BringToFront();

            return(frmInstance);
        }
        private void btnCargar_Click(object sender, EventArgs e)
        {
            try
            {
                var frmAdelantoCargar = FrmAdelantoCarga.Instance();
                frmAdelantoCargar.MdiParent = this.MdiParent;
                frmAdelantoCargar.Show();

                frmAdelantoCargar.frmList = this;
            }
            catch (Exception ex)
            {
                Util.ErrorMessage(ex.Message);
            }
        }