Beginning ASP.NET 4.5 in CSharp and VB Opsylum

544 x CHAPTER 14 LINQ AND THE ADO.NET ENTITY FRAMEWORK
accessing your site over a slow network connection. Instead of presenting them all the images in the
photo album on a single page, you can split up the photo album into multiple pages, enabling users
to go from page to page. You see how to do this in the next section, which discusses the DataPager
control.
Introducing the DataPager Control
The DataPager is a separate control that you can use to extend another, data-bound, control.
Currently, the .NET Framework lets you use the DataPager only to provide paging capabilities to
the ListView control, but the developer community has been active writing implementations for
other controls, like the GridView, as well.
You can hook up the DataPager to the ListView control in two ways: You can either define it
within the of the ListView control or you can define it entirely outside the
ListView. In the first case, the DataPager knows to what control it should provide paging capabilities
automatically. In the latter case, you need to set the PagedControlID property of the DataPager
to the ID of a valid ListView control. You see how to configure and use the DataPager in conjunction
with a ListView next. Being able to define the DataPager outside of the ListView control is
useful if you want to place it at a different location of the page, such as in the Footer or Sidebar
area, for example.
TRY IT OUT
Paging Data with the ListView and DataPager Controls
In this Try It Out you create the front-end page of the Gig Pics feature. Users of your site can choose
one of the available photo albums from a drop-down list and then view all the available pictures in a
pageable list that is created by a ListView and a DataPager control. Figure 14-22 shows the final result
of this exercise.
1. In the root of your site, create a new folder called PhotoAlbums. Inside this folder create a new
Web Form based on your custom page template and call it Default.aspx. Set the Title of the
page to All Photo Albums.
2. Switch to Design View and drop a DropDownList control on the page. On the control’s Smart
Tasks panel, enable AutoPostBack and then hook it up to a new EntityDataSource control by
clicking Choose Data Source, and then choosing from the first drop-down list.
Click the Entity icon, click OK, and select PlanetWroxEntities in the Named Connection dropdown
list. Click Next. On the Configure Data Selection dialog box, choose PhotoAlbums from the
EntitySetName drop-down list and select the fields Id and Name, as shown in Figure 14-20.
3. Click Finish to close the Configure Data Source wizard. In the Choose a Data Source dialog box,
select Name from the Data Field to Display drop-down list and leave Id selected in the Data Field
for the Value drop-down list. If you don’t see the items in the lists, click Refresh Schema first.
4. Click OK to close the Data Source Configuration Wizard.
5. Below the DropDownList add a new ListView control and connect it to a new EntityDataSource
by selecting from the drop-down list on the control’s Smart Tasks panel. Click
the Entity icon and click OK. Select PlanetWroxEntities in the drop-down and click Next. In the
dialog box that follows, choose Pictures from the EntitySetName drop-down list and click Finish.