private void TXT_DISCOUNT_KeyDown(object sender, KeyEventArgs e)
        {
            if(e.KeyCode==Keys.Enter)
            {
                if (ORDER.VERIFIY_QUANTITY(TXT_ID_PRODUCT.Text, Convert.ToInt32(TXT_QUA.Text)).Rows.Count < 1)
                {
                    MessageBox.Show(" الكميه المدخله لهذا المنتج غير متوفره", "تنبيه", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                    return;
                }

                for (int i=0;i<dataGridView1.Rows.Count-1;i++)
                {
                    if (dataGridView1.Rows[i].Cells[0].Value.ToString() == TXT_ID_PRODUCT.Text)
                    {
                        MessageBox.Show("هذا المنتج تم ادخاله مسبقا ", "تنبيه", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                        return; 

                    }
                    
                   
                }

                DataRow r = DT.NewRow();
                r[0] = TXT_ID_PRODUCT.Text;
                r[1] = TXT_NAME_PRODUCT.Text;
                r[2] = TXT_PRICE.Text;
                r[3] = TXT_QUA.Text;
                r[4] = TXT_AMOUNT.Text;
                r[5] = TXT_DISCOUNT.Text;
                r[6] = TXT_TO_AMOUNT.Text;
                DT.Rows.Add(r);
                dataGridView1.DataSource = DT;
                CLEAR_TXTS();
                button1.Focus();
                TXT_TOTAL_AMOUNT.Text =
                    (from DataGridViewRow row in dataGridView1.Rows
                     where row.Cells[6].FormattedValue.ToString() != string.Empty
                     select Convert.ToDouble(row.Cells[6].FormattedValue)).Sum().ToString();



                //double[] array = new double[dataGridView1.RowCount];
                //double summ = 0;
                //for (int i = 0; i < dataGridView1.Rows.Count-1; i++)
                //{
                //    //array[i] = Convert.ToDouble(dataGridView1.CurrentRow.Cells[6].Value.ToString());
                //    summ += Convert.ToDouble(dataGridView1.CurrentRow.Cells[6].Value.ToString());
                //}
                ////TXT_TOTAL_AMOUNT.Text = array.Sum().ToString();
                //TXT_TOTAL_AMOUNT.Text = summ.ToString();



            }
        }