ใช้งาน tooltip.Show(); แล้วมีปัญหาคือไม่สามารถ กด CellDoubleClick ได้ จะ error ตรง frm_emr_er.Show(); ช่วยดูให้หน่อยน่ะค่ะ

private void dgv_erpatientlist_CellDoubleClick(object sender, DataGridViewCellEventArgs e)
        {
            
            if (e.RowIndex != -1)
            {
                //Open Wait Form
                SplashScreenManager.ShowForm(this, typeof(master.frm_WaitForm), true, true, false);

                this.visitID = dgv_erpatientlist["VISIT_ID", e.RowIndex].Value.ToString();
                this.healingID = dgv_erpatientlist["HEALING_ID", e.RowIndex].Value.ToString();
                this.hnID = dgv_erpatientlist["HN_ID", e.RowIndex].Value.ToString();

                var frm_emr_er = new frm_emr_er(hnID, visitID, healingID);
                frm_emr_er.MdiParent = this.MdiParent;
                frm_emr_er.WindowState = FormWindowState.Maximized;

                //Close Wait Form
                SplashScreenManager.CloseForm(false);

                frm_emr_er.Show();
            }
        }
private void dgv_erpatientlist_CellMouseEnter(object sender, DataGridViewCellEventArgs e)
        {
            if (e.RowIndex != -1)
            {
                this.visitID = dgv_erpatientlist["VISIT_ID", e.RowIndex].Value.ToString();
                this.healingID = dgv_erpatientlist["HEALING_ID", e.RowIndex].Value.ToString();
                this.hnID = dgv_erpatientlist["HN_ID", e.RowIndex].Value.ToString();

                tooltip = new dlg_patientbox(hnID, visitID, healingID);                              

                tooltip.Show();
            }
        }

        private void dgv_erpatientlist_CellMouseLeave(object sender, DataGridViewCellEventArgs e)
        {
            tooltip.Close();
        }