private void FRM_PurchaseInvoice_Load(object sender, EventArgs e)
        {
            try
            {
                WareHouseManager.FillWareHouseComboBox(cmbWareHouse);
                VendorManager.FillVendorComboBox(cmbVendor);
                UnitManager.FillUnitComboBox(cmbUnit);

                HelperClass.FillSearchLookUpByData(cmbProduct, new ProductManager().CreateTable(), ProductManager.ProductDetails.ProductName.ToString(), ProductManager.ProductDetails.ProductCode.ToString());
                ProductList = new ProductManager().GetAll().ToList();
                btnAddNew_Click(null, null);
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }