Beginning ASP.NET 4.5 in CSharp and VB Opsylum

Updating and Inserting Data x 483
‰ Click the Manage Reviews link in the menu on the left.
‰ Select the right genre from the drop-down list at the top of the page. If you used the scripts
from the preceding chapter to create the data in your database, and you entered 1 for the
GenreId when inserting the review, the genre is Rap and Hip-Hop.
When you have found your review, you can click its title and you’ll be taken to AddEditReview
.aspx, where you can change the review’s details again.
How It Works
Most of this exercise should be familiar by now. The DetailsView works the same for inserting as
the DetailsView for genres you saw earlier. What’s different is how updates are handled. The code
in the Code Behind looks at the query string and if it finds an Id query string parameter, it flips the
DetailsView into edit mode:
VB.NET
If Request.QueryString.Get("Id") IsNot Nothing Then
DetailsView1.DefaultMode = DetailsViewMode.Edit
End If
C#
if (Request.QueryString.Get("Id") != null)
{
DetailsView1.DefaultMode = DetailsViewMode.Edit;
}
When the control is in edit mode, it knows what to do. It calls the SqlDataSource and requests its
data. The SqlDataSource in turn retrieves the ID of the review from the query string, accesses the
database, and then returns the correct review, which is displayed on the page. When you subsequently
click the Update link, the SqlDataSource fires its UpdateCommand to send the changes to the database.
This exercise provides a nice foundation for the following exercise, where you extend the
DetailsView by implementing custom templates with validation controls and set up various event
handlers to respond to the control’s events.
Right now, the page with the DetailsView looks quite dull. It would look a lot better and be easier
to use if it had the following features:
‰ A text area instead of a single-line text box for the Summary and Body fields
‰ A drop-down list for the genre filled with the available genres from the database
‰ Automatic updating of the UpdateDateTime column
‰ Validation controls to stop you from leaving required fields empty
‰ Automatic redirection to the Reviews.aspx page after an item has been inserted or updated
The next exercise shows you how to implement all of these features.