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ADO.NET: Part 2 – An Introduction to ADO.NET

Posted by Ravi Varma Thumati on November 4, 2009

What is ADO.NET?

ADO.NET is a set of libraries included with the Microsoft .NET Framework that helps you communicates with various data stores from .NET applications. The ADO.NET libraries include classes for connecting to a data source, submitting queries, and processing results. You can also use ADO.NET as a robust, hierarchical, disconnected data cache to work with data off line. The central disconnected objects, the DataSet, allow you to sort, search, filter, store pending changes, and navigate through hierarchical data. The DataSet also includes a number of features that bridge the gap between traditional data access and XML development. Developers can now work with XML data through traditional data access interfaces and vice-versa.

As an integral part of the .NET framework, it shares many of its features: such as multi-language support, garbage collection, just-in-time compilation, object-oriented design, and dynamic caching, and is far more than an upgrade of previous versions of ADO.

The ADO.NET classes are found in System.Data.dll, and are integrated with the XML classes found in System.Xml.dll. When compiling code that uses the System.Data namespace, reference both System.Data.dll and System.Xml.dll.

Evolution of ADO.NET 

The first data access model, DAO (data access model) was created for local databases with the built-in Jet engine which had performance and functionality issues. Next RDO (Remote Data Object) and ADO (Active Data Object) which were designed for Client Server architectures but soon ADO took over RDO.

ADO was a good architecture but as the language changes so is the technology. With ADO, all the data is contained in a recordset object which had problems when implemented on the network and penetrating firewalls. ADO was a connected data access, which means that when a connection to the database is established the connection remains open until the application is closed. Leaving the connection open for the lifetime of the application raises concerns about database security and network traffic; also, as databases are becoming increasingly important and as they are serving more people, a connected data access model makes us think about its productivity.

For example, an application with connected data access may do well when connected to two clients, the same may do poorly when connected to 10 and might be unusable when connected to 100 or more. Also, open database connections use system resources to a maximum extent making the system performance less effective.


ADO .NET addresses the above mentioned problems by maintaining a disconnected database access model which means, when an application interacts with the database, the connection is opened to serve the request of the application and is closed as soon as the request is completed. Likewise, if a database is updated, the connection is opened long enough to complete the Update operation and is closed. By keeping connections open for only a minimum period of time, ADO .NET conserves system resources and provides maximum security for databases and also has less impact on system performance. Also, ADO .NET when interacting with the database uses XML and converts all the data into XML format for database related operations making them more efficient.

Design Goals for ADO.NET

As application development has evolved, new applications have become loosely coupled based on the Web application model. More and more of today’s applications use XML to encode data to be passed over network connections. Web applications use HTTP as the fabric for communication between tiers, and therefore must explicitly handle maintaining state between requests. This new model is very different from the connected, tightly coupled style of programming that characterized the client/server era, where a connection was held open for the duration of the program’s lifetime and no special handling of state was required.

In designing tools and technologies to meet the needs of today’s developer, Microsoft recognized that an entirely new programming model for data access was needed, one that is built upon the .NET Framework. Building on the .NET Framework ensures that the data access technology would be uniform — components would share a common type system, design patterns, and naming conventions.

ADO.NET was designed to meet the needs of this new programming model: disconnected data architecture, tight integration with XML, common data representation with the ability to combine data from multiple and varied data sources, and optimized facilities for interacting with a database, all native to the .NET Framework.

In creating ADO.NET, Microsoft embraced the following design goals.

  • Leverage Current ADO Knowledge

The design for ADO.NET addresses many of the requirements of today’s application development model. At the same time, the programming model stays as similar as possible to ADO, so current ADO developers do not have to start from the beginning in learning a brand new data access technology. ADO.NET is an intrinsic part of the .NET Framework without seeming completely foreign to the ADO programmer.

ADO.NET coexists with ADO. While most new .NET-based applications will be written using ADO.NET, ADO remains available to the .NET programmer through .NET COM interoperability services.

  • Support the N-Tier Programming Model

ADO.NET provides first-class support for the disconnected, n-tier programming environment for which many new applications are written. The concept of working with a disconnected set of data has become a focal point in the programming model. The ADO.NET solution for n-tier programming is the DataSet.

  • Integrate XML Support

XML and data access are intimately tied — XML is all about encoding data, and data access is increasingly becoming all about XML. The .NET Framework does not just support Web standards — it is built entirely on top of them.

XML support is built into ADO.NET at a very fundamental level. The XML classes in the .NET Framework and ADO.NET are part of the same architecture — they integrate at many different levels. You no longer have to choose between the data access set of services and their XML counterparts; the ability to cross over from one to the other is inherent in the design of both.

Differences between ADO and ADO.NET

ADO and ADO.NET are different in several ways:

  • ADO works with connected data. This means that when you access data, such as viewing and updating data, it is real-time, with a connection being used all the time. This is barring, of course, you programming special routines to pull all your data into temporary tables.
  • ADO.NET uses data in a disconnected fashion. When you access data, ADO.NET makes a copy of the data using XML. ADO.NET only holds the connection open long enough to either pull down the data or to make any requested updates. This makes ADO.NET efficient to use for Web applications. It’s also decent for desktop applications.
  • ADO has one main object that is used to reference data, called the Recordset object. This object basically gives you a single table view of your data, although you can join tables to create a new set of records. With ADO.NET, you have various objects that allow you to access data in various ways. The DataSet object will actually allow you to store the relational model of your database. This allows you to pull up customers and their orders, accessing/updating the data in each related table individually.
  • ADO allows you to create client-side cursors only, whereas ADO.NET gives you the choice of either using client-side or server-side cursors. In ADO.NET, classes actually handle the work of cursors. This allows the developer to decide which is best. For Internet development, this is crucial in creating efficient applications.
  • Whereas ADO allows you to persist records in XML format, ADO.NET allows you to manipulate your data using XML as the primary means. This is nice when you are working with other business applications and also helps when you are working with firewalls because data is passed as HTML and XML.

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