Using the DataTable and DataView Classes

The DataTable class in ADO.NET represents a single database table. The DataView class represents a navigable view of data. It is still possible to send a heterogeneous query to a database and display the results in one table or view, but it is preferable to request tables individually in ADO.NET and express the interrelationships as a DataRelation object. As mentioned earlier, the latter technique yields a DataSet object that can be updated by writing changes to each independent table but displayed as if it contained a single set of heterogeneous data. Having complex master–detail relationships that are updatable is the best of both worlds.

We can use code similar to that in Listing 11.3 to demonstrate how to fill a DataTable. When we have a DataTable, we can request a DataView directly. We also have the option of populating the DataView directly. Listing 11.5 demonstrates how to populate a DataTable, and the next subsection demonstrates how to express master–detail relationships in a DataSet.

Listing 11.5. Populating a DataTable

Private Sub InitializeGridWithTable()

  Dim Connection As OleDbConnection = _
    New OleDbConnection(Database.ConnectionString)
  Dim Adapter As OleDbDataAdapter = _
    New OleDbDataAdapter("SELECT * FROM CUSTOMERS", Connection)

  Dim Customers As DataTable = New DataTable("Customers")
  Adapter.Fill(Customers)

  DataGrid1.DataSource = Customers
  DataGrid1.DataBind()

End Sub

To initialize the DataTable I copied and pasted the code from Listing 11.3 to create Listing 11.5, substituting a DataSet everywhere with a DataTable. When you have a DataTable you can request a DataView. The DataTable.DefaultView property will return the default DataView that represents the DataTable.

You also have the option of creating objects like DataSet, DataTable, and DataView programmatically, designing everything, and populating those ADO.NET elements from some source other than a database. In addition to ADO.NET working at a fundamental level with XML, ADO.NET uses data from providers, and a provider does not have to be a traditional database.