Let’s add an Extended Price field to show the final price of each line item in the order. This field will multiply price by quantity, and factor in the discount.
Switch to the Project Explorer, and select the Controllers tab. Expand OrderDetails, and right-click on Fields. Select New Field option.
For the new field, enter the following settings:
|The value of this field is computed at run-time by SQL Expression||True|
OrderDetails.UnitPrice * OrderDetails.Quantity * (1 - OrderDetails.Discount)
|Data Format String||c|
|Values of this field cannot be edited||True|
Press OK to save the field. The OrderDetails alias used in the SQL Expression field above is referring to command1 of the Order Details controller. The text of this command can be found at Order Details / Commands / command1 node.
Your application will incorporate the SQL Formula in the SELECT statements composed at runtime. The statement will be equivalent to the following simplified example.
select *, OrderDetails.UnitPrice * OrderDetails.Quantity * (1 - OrderDetails.Discount) ExtendedPrice from "Order Details" OrderDetails
This is the output produced in SQL Management Studio if you try executing the simplified statement.
To make sure that the field will be displayed in the application pages, we’ll bind the field to the data view using data fields. Go back to the field. Select the Data Fields tab. On the action bar, press New | New Tab.
Set the following settings for the data field:
|Category||New Order Details|
Press OK to save the data field. Use the same method to create two more data fields:
Regenerate the application, and navigate to Order Form page. Select an order. For each order detail, you will see a calculated Extended Price field.