Inventory System: Managing data using a database

Fig. 30 Hand in a filing cabinet.
CC BY-SA 4.0. By Watty62. Source: Wikimedia Commons

We will introduce databases for data input and output.

🤔 Question to ponder

1. What are the business data that we input in/ output from our inventory system?

2. How is data currently input and output?

3. What are the advantages & disadvantages of this approach?

Demo

Order processing with a database in the background. On the top, the tab `Order` shows the order data in the database. These are two orders by customers `Ramanda` and `Totoro`.

The video on the right shows three aspects of using a database:

1. When we process one order, this is reflected in the database after we refresh Order.

2. If we restart the program, then the state is preserved in the database

3. If we change the database data, we can change the data shown by the program

Requirements

1. Similar to previous week, build on the previous problem.

2. Your program must use a database called inventory.sqlite for getting the data for queued orders instead of static data through C#.

   Create the database using the example inventory data from last weeks.

3. If you used a Dict for Stock, then change it to a List of Items and introduce a Quantity in Item instead.

   The database framework we will use cannot navigate through dictionaries but lists.

4. Modify your class diagram if needed.

5. Record a demonstration of your project similar to the video on the right.

Tips

1. Read the database as the first step in MainWindow(). Otherwise orders may end up not being initialized which leads to empty list on the GUI

2. When reading the database, use .Include().ThenInclude statements to load aggregated classes. For example OrderBook needs to include QueuedOrders, which in turn needs to include OrderLines and finally OrderLines needs to include Item like this:

public void ReadDatabase()
{
    OrderBook = Db.OrderBooks
        .Include(o => o.QueuedOrders)
        .ThenInclude(o => o.OrderLines)
        .ThenInclude(o => o.Item)
        .Include(o => o.ProcessedOrders)
        .ThenInclude(o => o.OrderLines)
        .ThenInclude(o => o.Item)
        .ToList()[0];
}

1. Write to the database after processing each order.