Working with Data in ASP.NET 2.0 - Querying Data with the SqlDataSource Control
All of the tutorials we’ve examined so far have used a tiered architecture consisting of presentation, Business Logic, and Data Access layers. The Data Access Layer (DAL) was crafted in the first tutorial (Creating a Data Access Layer) and the Business Logic Layer in the second (Creating a Business Logic Layer). Starting with the Displaying Data With the ObjectDataSource tutorial, we saw how to use ASP.NET 2.0’s new ObjectDataSource control to declaratively interface with the architecture from the presentation layer. While all of the tutorials so far have used the architecture to work with data, it is also possible to access, insert, update, and delete database data directly from an ASP.NET page, bypassing the architecture. Doing so places the specific database queries and business logic directly in the web page. For sufficiently large or complex applications, designing, implementing, and using a tiered architecture is vitally important for the success, updatability, and maintainability of the application. Developing a robust architecture, however, can be overkill when creating exceedingly simple, oneoff applications.
ASP.NET 2.0 provides five builtin data source controls - SqlDataSource, AccessDataSource, ObjectDataSource, XmlDataSource, and SiteMapDataSource. The SqlDataSource can be used to access and modify data directly from a relational database, including Microsoft SQL Server, Microsoft Access, Oracle, MySQL, and others. In this tutorial and the next three, we’ll examine how to work with the SqlDataSource control, exploring how to query and filter database data, as well as how to use the SqlDataSource to insert, update, and delete data.
Comparing the ObjectDataSource and SqlDataSource
Conceptually, both the ObjectDataSource and SqlDataSource controls are simply proxies to data. As discussed in the Displaying Data With the ObjectDataSource tutorial, the ObjectDataSource has properties that indicate the object type that provides the data and the methods to invoke to select, insert, update, and delete data from the underlying object type. Once the ObjectDataSource’s properties have been configured, a data Web control - such as a GridView, DetailsView, or DataList - can be bound to the control, using the ObjectDataSource’s Select(), Insert(), Delete(), and Update() methods to interact with the underlying architecture.
The SqlDataSource provides the same functionality, but operates against a relational database rather than an object library. With the SqlDataSource, we must specify the database connection string and the adhoc SQL queries or stored procedures to execute to insert, update, delete, and retrieve data. The SqlDataSource’s Select(), Insert(), Update(), and Delete() methods, when invoked, connect to the specified database and issue the appropriate SQL query. As the following diagram illustrates, the these methods do the grunt work of connecting to a database, issuing a query, and returning the results.
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