private void cmdMonth_Click(object sender, EventArgs e) { this.Hide(); Form fc = Application.OpenForms["FRM_SMT_PU_PROD_MATERIAL_MONTH"]; if (fc != null) { fc.Show(); } else { FRM_SMT_PU_PROD_MATERIAL_MONTH f = new FRM_SMT_PU_PROD_MATERIAL_MONTH(); f.Show(); } }