The DataBind method in the BasePage class is overridden to read data from the database and bind this data to each user interface control. The page itself does not read the data, but instead delegates this responsibility to each of the controls within the page.

During the data binding phase, the table and record controls run the query and each child control will be individually data bound from the data that was retrieved by the query. The data binding lifecycle of each of the child controls with respect to their parent controls is shown below:

The data is retrieved into memory from each of the user interface controls and validated. The retrieved data is stored in an instance of the data access layer’s Record class.

Unlike reading data from the database, the saving of the data is accomplished at the page level instead of at the Table or Record control levels. This is because data from all records must be saved within a transaction and any foreign key relationships must be taken into account when the data is saved. For example, master records are saved first followed by child records since the child records need the Id of their parent record.

A number of events before and after writing the data to the database and before and after committing the transaction are available to you. If the Id’s of the records are assigned by the database, they will be available after the data is written to the database and before committing the transaction.

If the button action specifies redirection to another page, the Redirect method is called and can be overridden to change the URL parameters if needed. The Redirect method of the base class will automatically change the URL parameters if they have been specified in the Properties dialog box.

Page Class

You can access any user interface control from the page class except the controls that are repeated for each row in a table. To access the controls from the page, you simply specify the name of the control that is shown on the layout page. For example, if you have an Add Customer page, you may have a field label called CompanyNameLabel and a field value text box called CompanyName. To access this control, you can:

C#:

this.CompanyName this.CompanyName.Text             // to access the text entered by the user

VB.NET:

Me.CompanyName Me.CompanyName.Text             ' to access the text entered by the user

If you are displaying an Add, Edit or Show Record page, you will have a record control on the page as shown in the control hierarchy above. The record control corresponds to the record control class in the page’s code-behind file. If the page is a Show Table page, you will have a table control on the page and a record control for each row in the table. Both the table control and the record control will have corresponding classes in the page’s code-behind file. You can access the record and table controls within the page as follows:

C#:

this.CustomersRecord // to access the record control // to access the company name within the // record control      this.CustomersRecord.CompanyName      this.CustomersTable // to access the table control

VB.NET:

Me.CustomersRecord   ' to access the record control                    ' to access the company name within the                    ' record control Me.CustomersRecord.CompanyName Me.CustomersTable     ' to access the table control

Table Control Class

The table control class corresponds to the table control on the page. You can directly access all of the controls within the table except the rows of a table. To access the rows of a table, you can either override or handle events at the record control class level, or use functions such as GetRecordControls or GetRecords to get an array list that can loop through to get an individual row. The search, filter, pagination and column sorting controls can be accessed directly from the table control class.

Record Control Class

We recommend most of the code customizations to be made at the record control class. The record control class corresponds to the record being displayed on the page. If there is a table displayed on the page, the record control class corresponds to each row within a table. The customizations will be the same regardless of whether the record control class corresponds to a single record control or to a row within a table.

You can access all of the fields within a record control including column values as shown below:

C#:

this.CompanyName this.CompanyName.Text             // to access the text entered by the user

VB.NET:

Me.CompanyName Me.CompanyName.Text             ' to access the text entered by the user

C#:

if (!this.IsPostBack) {      // done only during initialization } else {      // done only during postback }

VB.NET

If (Not Me.IsPostBack) Then     ' done only during initialization Else     ' done only during postback End If

Mr. Mohiuddin co-founded numerous Internet and software companies, including Onsale, Inc. (later Egghead.com and now Amazon.com), Ambia Corporation, an electronic document publishing software company later acquired by Infodata Systems Inc., and Software Partners, Inc., a software consulting company that developed StreetSmart, e.Schwab, FundMap, SchwabLink and Retirement Planner software for Charles Schwab & Co.

Mr. Mohiuddin earned his BS in Computer Science from the University of Illinois, Chicago.