Saturday, September 29, 2012

“Select” Action

The application framework initiates a Select action when a data view needs to load data from the server.

Let’s create an example using a Northwind sample web app to see when the Select action is fired in the server code.

Start the Project Designer. In the Project Explorer, switch to the Controllers tab and right-click on Orders / Business Rules node. Press New Business Rule.

New Business Rule context menu option in the Project Explorer.

Give this rule the following properties:

Property Value
Type SQL
Command Name Select
Phase Before
Script
set @Result_ShowAlert = 'Before'

Press OK to save the business rule. Right-click Orders / Business Rules and press New Business Rule again.

New Business Rule context menu option in the Project Explorer.

Assign these properties:

Property Value
Type SQL
Command Name Select
Phase Execute
Script
set @Result_ShowAlert = @CustomerCompanyName

Press OK to save. Create one more business rule with this configuration:

Property Value
Type SQL
Command Name Select
Phase After
Script
set @Result_ShowAlert = 'After'

Press OK to save. The Business Rules node should look like the picture below.

image

Assigning a value to @Result_ShowAlert creates a JavaScript expression that is added to the server response. As a page of data is rendered, the “alert” expressions will be consequently appended to the ClientScript property of the Result.

The client library will evaluate the entire ClientScript property content using eval function of JavaScript language. This will result in the sequence of alerts displayed to the user.

On the toolbar, press Browse.

Navigate to the Orders page. The first popup for Before phase will appear.

Alert showing 'Before' appears before the select command occurs.

Press OK, and alert for Execute phase will appear, showing the Customer Company Name of the first record.

Alert displaying the Customer Company Name of the data being selected.

Keep pressing OK, as each alert will display the Customer Company Name of each record displayed in the grid. After alerts for each selected data row have been displayed, the After phase popup will appear.

Alert displaying 'After' when the select command has been completed.

Click on a Customer Company Name link. The three alerts will appear in succession as well.

Alert displaying 'Before' when user navigates to the form view of an order.

When you press Edit in the form, no alerts will be shown – this is because Edit command only renders the form on the client without making a round trip to the server. The data has already been retrieved from the server when select command was fired.

No alert is displayed when the form enters edit mode - Edit command does not travel to the server.

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