Databases Reference
In-Depth Information
<asp:EntityDataSource ID=”dataSource” runat=”server”
EnableDelete=”true”
/>
<asp:QueryExtender TargetControlID=”dataSource” runat=”server”>
<asp:DynamicRouteExpression />
</asp:QueryExtender>
</ContentTemplate>
</asp:UpdatePanel>
</asp:Content>
The only substantial difference between this new Delete template and the built-in Details
template is the set of button and link controls. The new Delete template uses a
Button
control instead of a
LinkButton
to make confirmation of deletion visually different from
merely requesting it. It also does not have an Edit link the Details page template uses to
take users to the Edit page.
Although they might seem unnecessary, the
ValidationSummary
and
DynamicValidator
controls still play an important role in the Delete page template. If the user tries to delete
a Customer who placed one or more orders, a database error will occur due to a foreign
key constraint violation. As discussed in Chapter 8, database errors can be presented to the
Dynamic Data as instances of the
ValidationException
class. The
DynamicValidator
control at the top of the page automatically displays unhandled
ValidationException
errors in the
ValidationSummary
instead of generating a yellow screen of death.
After implementing the new Delete page template, you also need to modify the
existing
templates to redirect the user to a new dynamic page generated by the new template
instead of displaying the JavaScript prompt. In both List and Details page templates,
replace the following
LinkButton
:
<asp:LinkButton runat=”server” CommandName=”Delete” Text=”Delete”
OnClientClick='return confirm(“Are you sure you want to delete this
item?”);'/>
with the following
DynamicHyperLink
control:
<asp:DynamicHyperLink runat=”server” Action=”Delete” Text=”Delete” />
And because the Details page will no longer delete the records, you can remove the
EnableDelete
property from its
EntityDataSource
control in page markup and remove
the
ItemDeleted
event handler from the
FormView
control in the code-behind.
Figure 6.7 shows an example of the dynamically generated Delete page for the Product
entity type. The entity itself (labels and field values) looks similar to the dynamically
generated Details page, which is a great example of how page templates allow you to
implement different actions and data access logic while reusing the common presentation
logic encapsulated by the entity templates.
