private void frmPurchaseOrder_Load(object sender, EventArgs e) { DataTable dt = bllss4.getAllSuppliers(); comboBox1.DataSource = dt; comboBox1.DisplayMember = "SupplyName"; comboBox1.ValueMember = "ID"; DataTable dt1 = bllss4.getAllWareHouses(); comboBox2.DataSource = dt1; comboBox2.DisplayMember = "WareHouseName"; comboBox2.ValueMember = "ID"; DataTable dt2 = bllss4.getAllPart(); comboBox3.DataSource = dt2; comboBox3.DisplayMember = "PartName"; comboBox3.ValueMember = "ID"; textBox1.Enabled = false; }