ActiveX Data Object.NET (ADO.NET)

ActiveX Data Object.NET (ADO.NET) is a software library in the .NET framework consisting of software components providing data access services. ADO.NET is designed to enable developers to write managed code for obtaining disconnected access to data sources, which can be relational or non-relational (such as XML or application data). This feature of ADO.NET helps to create data-sharing, distributed applications.

ADO.NET provides connected access to a database connection using the .NET-managed providers and disconnected access using datasets, which are applications using the database connection only during retrieval of data or for data update. Dataset is the component helping to store the persistent data in memory to provide disconnected access for using the database resource efficiently and with better scalability.

ADO.NET evolved from ADO, which is also a technology similar to ADO.NET with a few basic structural changes. Although there is a provision to work in disconnected mode using ADO, data is transmitted to the database in ADO.NET more efficiently using data adapters. The in-memory representation of data differs between ADO and ADO.NET. ADO.NET can hold the data in a single result table, but ADO holds multiple tables along with their relationship details. Unlike ADO, data transmission between applications using ADO.NET does not use COM (component object model) marshalling but uses dataset, which transmits data as an XML stream.

The architecture of ADO.NET is based on two primary elements: DataSet and .NET framework data provider.

Dataset provides the following components:

1. a complete set of data including related tables, constraints and their relationships
2. functionality-like access to remote data from XML Web service
3. manipulation of data dynamically
4. data processing in a connectionless manner
5. provision for hierarchical XML view of relational data
6. usage of tools like XSLT and XPath Query to operate on the data

The .NET framework data provider includes the following components for data manipulation:

• Connection: This provides connectivity to the data source
• Command: This executes the database statements needed to retrieve data, modify data or execute stored procedures.
• DataReader: This retrieves data in forward only and read-only form.
• DataAdapter: This acts as bridge between dataset and data source to load the dataset and reconcile changes made in dataset back to the source.

ADO.NET entity framework of .NET framework 4.0, the new technology of ADO.NET, abstracts the level of data programming so as to eliminate the impedance mismatch between data models and languages, which application developers would otherwise have to deal with.