Many Web applications work with a middle tier, or business layer, for retrieving and working with application data. This middle tier encapsulates database code inside of classes. Web developers can then call methods on these classes to select, insert, modify, and delete data.
The XmlDataSource control provides a means to create a binding connection between controls on your page and an XML file. The XML data source control is best used when you wish to bind to XML data that is represented as hierarchical (such as using in the TreeView control).
透過 ADO.NET 我們可以利用程式碼建立資料庫連線以存取資料，這些程式碼通常會被建立在抽象的 DAL 或 BLL 層。 若須求只有簡單的建立連線與存取資料，我們也可以透過資料來源控制項來實現，而不用使用 ADO.NET 。 它可以存取的對象包括 objects, XML, and databases 。
