Unveil the Data Binding Architecture inside Microsoft ASP.NET Ajax 1.0 - Part 1
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by Xianzhong Zhu
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Introduction to the client-side controls in namespace Sys.Preview.UI.Data

ItemView control

We need to display user a detailed view about our items in a collection, such as the details about your product in a shopping application. The MS AJAX client-side control ItemView provides this feature for you, just like the ASP.NET server control DetailsView behaviors, but it runs totally on the client side. The ItemView class and ListView class both inherit from base classSys.UI.Data.DataControl, which provides the basic functionalities of a DataControl, including many additional properties.

There are several client-side controls in namespace Sys.Preview.UI.Data, such as DataControl (the parent control of ItemView and ListView), DataNavigator, ItemView, ListView, XSLTView, etc.

Here, we merely concentrate on two controlsItemView and ListView. In practice, as the ASP.NET server control GridView is to ObjectDataSource, so is the MS AJAX client-side control ItemView (or ListView) to DataSource. And also, there exist similar data bindings between the two couples. The following table lists the commonly used and self-defined properties with their short explanations in column two.

Property name

Description

id

Identifying the ItemView control.

canMoveNext

There’s a next record you can move to if true; or else false.

canMovePrevious

There’s a previous record you can move to if true; or else false.

data

It holds all the Sys.Preview.Data.DataTable objects loaded into current ItemView controlthese DataTable objects are obtained from the background by the DataSource control.

dataIndex

Identifies the current record index.

dataItem

Returns the current record based on dataIndex.

Length

Returns the count of all records.

itemTemplate

This template is used for rendering a single item in the list (e.g., use a <tr> tag). It must be contained in the layoutTemplate.

EmptyTemplate

This template is used for rendering an empty message if there’s no item in the data source, or the ItemView is still waiting for the data from server.

Commonly used methods in ItemView

Method name

Description

addItem

adds a new item to the data collection on the client side, and this operation will make the dataset dirty

deleteCurrentItem

deletes current item from the data collection on the client side, and this operation will also make the dataset dirty

moveNext

moves to the next record, and this operation will again t rigger the data binding for the controls defined inside ItemTemplate

movePrevious

moves to the previous record, and this operation will again trigger the data binding for the controls defined inside ItemTemplate

Please note all the operations above are at client side, which just modify the client side data. So if you want to commit the changes to server, you have to call the methods in DataSource.

Obviously, the ItemView is always used to display one record on the client side, while the ListView control discussed next is for listing records within a range satisfying some condition.

ListView control

In most of the current web applications you often have to find a way to show user a table of data. Just as the ASP.NET GridView server control does, MS AJAX ListView control provides the same behavior on client side in the AJAX way. Although you can use traditional ASP.NET 2.0 GridView server control and then simply add an MS AJAX UpdatePanel to let your GridView work in the AJAX way, but this is with low efficiency and not the ‘pure’ MS AJAX way. You may need to use the full client-side MS AJAX control ListView to make things better. Do not be afraid, this is just as simple as the GridView with similar concepts such as ItemTemplate, but keep in mind there’s no IntelliSense provided by the IDE, and so you must pay more attention on typing the code.

Author's Note: In the new Visual Studio "Orcas" JavaScript Intellisense is supported for MS AJAX.

Commonly used properties in ListView

Property name

Description

Id

Identifes the ListView control.

canMoveNext

There’s a next record you can move to if true; or else false.

canMovePrevious

There’s a previous record you can move to if true; or else false.

Data

Same as that of ItemView

dataIndex

Identifying the current record index.

dataItem

Returning the current record based on dataIndex.

Length

Returning record count.

alternatingItemCssClass

Specify the CSS class for alternating items.

layoutTemplate

This template is used for rendering the list container (e.g., use a <table> tag), header (e.g., use a <thead> tag) and footer. You must specify a layoutTemplate for a ListView. This template must contain an itemTemplate, and may contain a separatorTemplate.

itemCssClass

Specify the CSS class for items.

itemTemplate

This template is used for rendering a single item in the list (e.g., use a <tr> tag). It must be contained in the layoutTemplate.

EmptyTemplate

This template is used for rendering an empty message if there’s no item in the data source, or the ListView is still waiting for the data from server.

selectedItemCssClass

Specify the CSS class for selected items.

seperatorCssClass

Specify the CSS class for separators.

seperatorTemplate

This template is used for rendering a separator between items in the list (e.g., use a <hr> tag). It must be contained in the layoutTemplate.

itemTemplateParentElementID

This property defines the parent element of itemTemplate and separatorTemplate. So the items and separators can be repeated in this element (e.g., use a <tbody> tag).

As with ItemView, to use a ListView, you have to provide MS AJAX some templates above to let it know how to render your content. In practice, these templates are generally corresponding to some special HTML elements, such as "<div>", so be careful.

Indeed, enough of theory debate now. So, let's roll up our sleeves and write a simple example!


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