Professional Visual Studio® 2008

21.1. DataSet Overview

The .NET Framework DataSet is a complex object that is approximately equivalent to an in-memory representation of a database. It contains DataTables that correlate to database tables. These in turn contain a series of DataColumns that define the composition of each DataRow. The DataRow correlates to a row in a database table. Of course, it is possible to establish relationships between DataTables within the DataSet in the same way that a database has relationships between tables.

One of the ongoing challenges for the object-oriented programming paradigm is that it does not align smoothly with the relational database model. The DataSet object goes a long way toward bridging this gap, because it can be used to represent and work with relational data in an object-oriented fashion. However, the biggest issue with a raw DataSet is that it is weakly typed. Although the type of each column can be queried prior to accessing data elements, this adds overhead and can make code very unreadable. Strongly typed DataSets combine the advantages of a DataSet with strong typing to ensure that data is accessed correctly at design time. This is done with the custom tool MSDataSetGenerator, which converts an XML schema into a strongly typed DataSet, essentially replacing a lot of runtime type checking with code generated at design time. In the following code snippet, you can see the difference between using a raw DataSet, in the first half of the snippet, and a strongly typed ...