The ADO.Net DataSet Object Part 1

The DataSet is an in-memory database – a collection of virtual tables with means to populate, examine, modify and deleting delete the tables and the data within them. You can also define and manipulate the relationships between the tables and tables, create and enforce constraints to maintain those relationships. Surprisingly, the data that populates the tables within a DataSet can and frequently does come from different data sources, leading to very powerful flexibility in connecting and maintaining data in various server sources.

The primary purpose of a DataSet is to allow the user to operate on data from a server in a disconnected mode. The temporary separation of data from the server is a desirable thing because it frees memory on the server, as well as connection and network resources. The DataSet allows data to be ‘borrowed’ from the server in relatively small usable chunks. The DataSet then ‘manages’ the connection between the data and allows the user to edit, update, delete, append, or select portions of that data.

The DataSet is first and foremost a collection of table objects. These table objects can be imported from various and diverse data sources such as SQL Server, Oracle, XML files, and the like, or they can be entered programmatically or through a convenient User Interface (UI) and then added to the DataSet programmatically. The most useful methods are to Accept Changes, AcceptChanges, RejectChanges, Merge, Clone, a few functions for reading and writing XML and XML schema, and – most important of all- the GetChanges method, which gets a DataSet which contains all of the data changes made to the current one since it was loaded.

The table objects look like tables in a regular database, though they are virtual tables, which reside only in memory. The table objects have collections of DataColumns, DataRows, Constraints, DataRelations, Property Collections, DataRowView, and a PrimaryKey, which may be a collection of DataColumns.

DataTable Class Members

Constructors Visibility Constructor Parameters       public DataTable ( )       public DataTable ( String tableName )       Properties February 11, 2008 Visibility Name Value Type Accessibility         public CaseSensitive Boolean [ Get , Set ]         public ChildRelations DataRelationCollection [ Get ]         public Columns DataColumnCollection [ Get ]         public Constraints ConstraintCollection [ Get ]         public Container IContainer [ Get ]         public DataSet DataSet [ Get ]         public DefaultView DataView [ Get ]         public DesignMode Boolean [ Get ]         public DisplayExpression String [ Get , Set ]         public ExtendedProperties PropertyCollection [ Get ]         public HasErrors Boolean [ Get ]         public Locale CultureInfo [ Get , Set ]         public MinimumCapacity Int32 [ Get , Set ]         public Namespace String [ Get , Set ]         public ParentRelations DataRelationCollection [ Get ]         public Prefix String [ Get , Set ]       public PrimaryKey DataColumn [ Get , Set ]         public Rows DataRowCollection [ Get ]         public Site ISite [ Get , Set ]         public TableName String [ Get , Set ]         Methods Visibility Name Parameters Return Type         public AcceptChanges ( ) Void         public BeginInit ( ) Void         public BeginLoadData ( ) Void         public Clear ( ) Void         public Clone ( ) DataTable         public Compute ( String expression , String filter ) Object         public Copy ( ) DataTable         public EndInit ( ) Void         public EndLoadData ( ) Void         public GetChanges ( DataRowState rowStates ) DataTable         public GetChanges ( ) DataTable         public GetErrors ( ) DataRow         public ImportRow ( DataRow row ) Void         public LoadDataRow ( Object values , Boolean fAcceptChanges ) DataRow         public NewRow ( ) DataRow         public RejectChanges ( ) Void         public Reset ( ) Void         public Select ( String filterExpression , String sort , DataViewRowState recordStates ) DataRow         public Select ( String filterExpression ) DataRow         public Select ( ) DataRow         public Select ( String filterExpression , String sort ) DataRow         public ToString ( ) String         Events Multicast Name Type       multicast ColumnChanged DataColumnChangeEventHandler       multicast ColumnChanging DataColumnChangeEventHandler       multicast Disposed EventHandler       multicast RowChanged DataRowChangeEventHandler       multicast RowChanging DataRowChangeEventHandler       multicast RowDeleted DataRowChangeEventHandler       multicast RowDeleting DataRowChangeEventHandler

Rows are added programmatically using the DataRows object:

 

Dim dr as DataRow=tblEmployee.NewRow()

dr(“dcFirstName”)=”Elmer”

dr(“dcLastName”)=”Fudd”

tblEmployee.Rows.Add(dr)

 

 

Resources

• Tutorial: ADO.NET Populate a DataSet from a Database

This tutorial discusses populating a DataSet from a Database.

• Tutorial: DataSet Vs. DataReader

This is an interesting resource that discusses DataSet and Datareader.