Dataset has a collection of Data Table object within the Tables collection. Each Data Table object contains a collection of Data Row objects and a collection of Data Column objects. There are also collections for the primary keys, constraints, and default values used in this table, which is called as constraint collection, and the parent and child relationships between the tables. Finally, there is a Default View object for each table. This is used to create a Data View object based on the table, so that the data can be searched, filtered, or otherwise manipulated while displaying the data.

The DataSet class exists in the System.Data namespace. The Classes contained in the DataSet class are:

DataTable 
DataColumn
DataRow 
Constraint
DataRelation

A candidate key is acombination of attributes that can be uniquely used to identify a database record.Each table may have one or more candidate keys.One of these candidate keys is selected as the primary key

Objects in Dataset:

Dataset has a collection of DataTable object within the Tables collection. Each DataTable object contains a collection of DataRow objects and a collection of DataColumn objects. There are also collections for the primary keys, constraints, and default values used in this table which is called as constraint collection, and the parent and child relationships between the tables. Finally, there is a DefaultView object for each table. This is used to create a DataView object based on the table, so that the data can be searched, filtered or otherwise manipulated while displaying the data.