The DataSet class exists in the System.Data namespace.
|DataTable||It is defined in the System.Data namespace and represents a single table of memory-resident data. It contains a collection of columns represented by a DataColumnCollection. Constraints represented by a ConstraintCollection. It also contains a collection of rows represented by the DataRowCollection.|
|DataColumn||Relationships can be built with more than one column per table by specifying an array of DataColumn objects as the key columns.|
|DataRow||It retains both its current and original versions to identify changes to the values stored in the row.|
|Constraint||It adds a UniqueKeyConstraint or a ForeignKeyConstraint to enforce an integrity constraints when changes are made to the related column values.|
|DataRelation||It identifies matching columns in two tables of a DataSet.|