private void txtDiscount_KeyDown(object sender, KeyEventArgs e) { if (e.KeyCode == Keys.Enter) { if (order.VerifyQty(txtIDproduct.Text, Convert.ToInt32(txtQty.Text)).Rows.Count < 1) { MessageBox.Show("الكمية المدخلة لهذا المنتج غير متاحة", "تنبيه", MessageBoxButtons.OK, MessageBoxIcon.Exclamation); return; } for (int i = 0; i < dgvProducts.Rows.Count - 1; i++) { if (dgvProducts.Rows[i].Cells[0].Value.ToString() == txtIDproduct.Text) { MessageBox.Show("هذا المنتج تم إدخاله مسبقا", "تنبيه", MessageBoxButtons.OK, MessageBoxIcon.Exclamation); return; } } DataRow r = Dt.NewRow(); r[0] = txtIDproduct.Text; r[1] = txtNameProduct.Text; r[2] = txtPrice.Text; r[3] = txtQty.Text; r[4] = txtAmount.Text; r[5] = txtDiscount.Text; r[6] = txtTotalAmount.Text; Dt.Rows.Add(r); dgvProducts.DataSource = Dt; ClearBoxes(); txtSumTotals.Text = (from DataGridViewRow row in dgvProducts.Rows where row.Cells[6].FormattedValue.ToString() != string.Empty select Convert.ToDouble(row.Cells[6].FormattedValue)).Sum().ToString(); } }