Beginning ASP.NET 4.5 in CSharp and VB Opsylum

536 x CHAPTER 14 LINQ AND THE ADO.NET ENTITY FRAMEWORK
The code in the ListView uses Eval and Bind statements to get data in and out of the Picture objects
that you’re assigning to the controls. ASP.NET 4.5 introduces a new way to set up these bindings, as
you see next.
Using Strongly Typed Data-Bound Controls
When VS created the code for the ListView for you, it added Bind and Eval statements like this:
...
As you learned in the “How It Works” section of the preceding exercise, Bind is for two-way data
binding (for insert and edit scenarios) and Eval is for read-only scenarios. Notice how the name of
the property (ToolTip in this example) is a literal string placed between quotes. Using string literals
makes your code more prone to errors. First of all, it’s easy to misspell the name. Because a string
cannot be checked by VS at development time, you won’t notice this error until you view the page in
the browser. Secondly, if you rename a property, the change is not picked up by the string literal.
Fortunately, ASP.NET 4.5 now has a solution to deal with this problem. The data-bound controls
(such as the ListView, the Repeater, the GridView, the DetailsView, and the FormView) have
been turned into strongly typed data-bound controls. They have been extended with an ItemType
property that you can point to the type of object you’re assigning to its data source. In the preceding
example, this type would have been PlanetWroxModel.Picture, the fully qualified name of the
Picture class. Once you’ve set this property, the data-bound control gets two new properties, Item
and BindItem, that are of the type you assigned to the ItemType property. The first one serves as a
replacement for Eval and the second one replaces Bind. By setting the ItemType property and using
Item and BindItem, you get the following benefits:
‰ IntelliSense now helps you find the correct property of the object you’re working with, as
shown in Figure 14-17.
FIGURE 14-17
‰ When you now misspell the name of a property, or rename it later, you get an error in the
Error List, giving you the chance to fix the problem before the page is viewed in the browser.
‰ External tools (available for the full versions of Visual Studio) will correctly rename the item
in the markup when you rename a property on your object.