Building Templated Databound Controls

Creating Templated Controls

A template enables you to customize the layout of a control. Furthermore, a template can contain expressions that are not evaluated until runtime. The ASP.NET Framework supports two types of templates. First, you can create a one-way databinding template. You use a one-way databinding template to display data items. In a one-way databinding template, you use the Eval() expression to display the value of a data item.

Second, you have the option of creating a two-way databinding template. A two-way databinding template can be used not only to display data items, but also to update data items. You can use the Bind() expression in a two-way databinding template to both display a data item and extract the value of a data item. Typically, you use templates with a databound control. For example, the ListView, GridView, Repeater, DataList, FormView, and DetailsView controls all support an ItemTemplate that enables you to format the data items that these controls display.

Implementing the ITemplate Interface

You create a one-way databinding template by adding a property to a control that returns an object that implements the ITemplate interface. The ITemplate interface includes one method:

InstantiateIn—Instantiates the contents of a template in a particular control.

Building Custom Control

You must answer two questions before writing a custom control:

What type of control do I want to write?

From what class do I inherit?

The two basic types of controls are fully rendered and composite controls. When you build a fully rendered control, you start from scratch. You specify all the HTML content that the control renders to the browser. When you create a composite control, on the other hand, you build a new control from existing controls. For example, you can create a composite AddressForm control from existing TextBox and RequiredFieldValidator controls. When you create a composite control, you bundle together existing controls as a new control. The second question that you must address is the choice of the base control for your new control. You can inherit a new control from any existing ASP.NET control. For example, if you want to create a better GridView control, then you can inherit a new control from the GridView control and add additional properties and methods to your custom GridView control.

Typically, when building a basic control, you inherit your new control from one of the following base classes:

. System.Web.UI.Control

. System.Web.UI.WebControls.WebControl

. System.Web.UI.WebControls.CompositeControl

Configuring Applications

ASP.NET uses a hierarchical system of configuration. At the top of the hierarchy is the Machine.config file. This file contains all the default configuration settings for ASP.NET applications and all other types of applications built with the .NET Framework.

The Machine.config file is located at the following path:

C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\CONFIG\Machine.config

This same folder also contains a Web.config file. The Web.config file contains settings specific to ASP.NET applications. The Web.config file overrides particular settings in the Machine.config file.

The \CONFIG folder includes the following six files:

Machine.config—Contains the actual configuration settings.

Machine.config.default—Contains the default values for all configuration settings.

Machine.config.comments—Contains comments on each configuration setting.

Web.config—Contains the actual configuration settings.

Web.config.default—Contains the default values for all configuration settings.

Web.config.comments—Contains comments on each configuration setting.

Only the Machine.config and Web.config files are actually used. The other files are there for the purpose of documentation. You can place a Web.config file in the root folder of a website, such as the wwwroot

folder. A Web.config file located in the root folder of a website contains settings that apply to all applications contained in the website. You also can place a Web.config file in the root of a particular application. In that case, the Web.config file has application scope. Finally, you can place a Web.config file in an application subfolder. In that case, the Web.config file applies to all pages in that folder and below.

Working with the HTTP Runtime

Creating a Custom BuildProvider

When you write an ASP.NET page and save the page to your computer’s file system, the ASP.NET page gets compiled dynamically into a .NET class in the background. The page is compiled dynamically by a BuildProvider. The ASP.NET Framework includes a number of BuildProviders. Each BuildProvider is responsible for compiling a file with a particular extension that is located in a particular type of folder. For example, there are BuildProviders for Themes, Master Pages, User Controls, and Web Services. When a BuildProvider builds, it builds a new class in the Temporary ASP.NET Files folder. Any class added to the folder becomes available to your application automatically. When you use Visual Web Developer, any public properties and methods of the class appear in Intellisense.

You can create your own BuildProviders. This can be useful in a variety of different scenarios. For example, imagine that you find yourself building a lot of ASP.NET pages that display forms. You can tediously build each ASP.NET page by hand by adding all the necessary form and validation controls. Alternatively, you can create a new BuildProvider that takes an XML file and generates the form pages for you automatically.

Localizing Applications for Multiple Languages

One can localize an ASP.NET website so that it supports multiple languages and cultures. For example, you might need to create both an English language and Spanish language version of the same website.

One approach to localization is to simply create multiple copies of the same website and translate each copy into a different language. This is a common approach when building ASP Classic (or even ASP.NET 1.1) websites. The problem with this approach is it creates a website maintenance nightmare. Whenever you need to make a change to the website—no matter how simple—you must make the change in each copy of the website. When building ASP.NET applications, you do not need to create multiple copies of a website to support multiple languages. Instead, you can take advantage of resource files. A resource file contains language-specific content. For example, one resource file might contain a Spanish version of all the text in your website, and a second resource file might contain the Indonesian version of all the text in your website.

Setting the Current Culture

Two main properties of the Page class have an effect on localization:

UICulture

Culture