Updaing Command not updating Gridview

Please can someone help me with this update command, i think i got it wrong its not updating gridview:

con9 = new SqlConnection(cs); con9.Open(); //updating the record SqlCommand cmd4 = new SqlCommand("UPDATE [Customer_Order] SET [OrderDate] = @OrderDate, [Branch] = @Branch, [Posted_By] = @Posted_By, [CustomerID] = @CustomerID, [Payment_Methode] = @Payment_Methode, [Product_Code] = @Product_Code, [Category] = @Category, [Brand] = @Brand, [Delivery_Manager] = @Delivery_Manager, [Quantity_By_Customer] = @Quantity_By_Customer, [Discount] = @Discount, [Unit_Price] = @Unit_Price, [Bank_Name] = @Bank_Name, [Delivery_Location] = @Delivery_Location, [Delivery_Date] = @Delivery_Date, [Total_Cost] = @Total_Cost, [Ground_Total] = @Ground_Total WHERE [Invoice_No] = @Invoice_No", con9); //SqlCommand cmd4 = new SqlCommand("Update Customer_Order set Posted_By='" + txtPostedby.Text + " ...