private void CodeTextBox_TextChanged(object sender, EventArgs e)
        {
            _modelPurchase.ProductCode = codeTextBox.Text;

            if (_purchaseManager.IsCodeExits(_modelPurchase))
            {
                availAbleQtyTextBox.Text = _purchaseManager.AvaiableQuantity(_modelPurchase).ToString();
                previousUnitTextBox.Text = _purchaseManager.PreviousUnitPrice(_modelPurchase).ToString();
                previousMrpTextBox.Text  = _purchaseManager.PreviousMRP(_modelPurchase).ToString();
            }
            else
            {
                availAbleQtyTextBox.Text = "0";
                previousUnitTextBox.Text = "0";
                previousMrpTextBox.Text  = "0";
                return;
            }



            //if (string.IsNullOrEmpty(availAbleQtyTextBox.Text))
            //{
            //    availAbleQtyTextBox.Text = 0.ToString();
            //}
            //else
            //{
            //    availAbleQtyTextBox.Text = _purchaseManager.AvaiableQuantity(_modelPurchase).ToString();
            //}



            //availAbleQtyTextBox.Text = _purchaseManager.Qty(_modelPurchase).ToString();

            //int qty = 0;
            ////int availableQty = 0;

            //for (int i = 0; i < _purchaseManager.AvaiableQuantity(_modelPurchase).Count; i++)
            //{
            //    qty = i + _modelPurchase.Quantity;
            //    //availableQty = qty + 1;
            //}
            //availAbleQtyTextBox.Text = qty.ToString();
        }