DataSet class is ADO.NET’s
highly flexible, general-purpose mechanism for reading and updating
data. Example 8-1 shows how to issue a
SELECT statement against the SQL Server
Northwind sample database
to retrieve and display the names of companies located in London. The
resulting display is shown in Figure 8-1.
Figure 8-1. The output generated by the code in Example 8-1
Example 8-1. Retrieving data from SQL Server using a SQL SELECT statement
' Open a connection to the database. Dim strConnection As String = _ "Data Source=localhost; Initial Catalog=Northwind;" _ & "Integrated Security=True" Dim cn As SqlConnection = New SqlConnection(strConnection) cn.Open( ) ' Set up a data set command object. Dim strSelect As String = "SELECT * FROM Customers WHERE City = 'London'" Dim dscmd As New SqlDataAdapter(strSelect, cn) ' Load a data set. Dim ds As New DataSet( ) dscmd.Fill(ds, "LondonCustomers") ' Close the connection. cn.Close( ) ' Do something with the data set. Dim dt As DataTable = ds.Tables.Item("LondonCustomers") Dim rowCustomer As DataRow For Each rowCustomer In dt.Rows Console.WriteLine(rowCustomer.Item("CompanyName")) Next
The code in Example 8-1 performs the following steps to obtain data from the database:
Opens a connection to the database using a SqlConnection object.
Instantiates an object of type SqlDataAdapter in preparation for filling ...