Programming Visual Basic .NET, Second Edition

Getting Started with ADO.NET

Enough theory! Let’s write some code and see how this works. Working with ADO.NET can be complex, but for many queries, the model is surprisingly simple.

In this example, you’ll create a simple Windows Form, with a single listbox in it called lbCustomers. You’ll populate this listbox with bits of information from the Customers table in the Northwind database.

Begin by creating a DataAdapter object:

Dim myDataAdapter As New SqlDataAdapter( _
  commandString, connectionString)

The two parameters are commandString and connectionString. The commandString is the SQL statement that will generate the data you want in your DataSet:

Dim commandString As String = _
  "Select CompanyName, ContactName from Customers"

The connectionString is whatever string is needed to connect to the database. In my case, I’m running SQL Server on my development machine where I have left the system administrator (sa) password blank (I know, I know, not a good idea. I’ll fix it by the time this book is released. Honest.):

Dim connectionString As String = _
    "server=localhost; uid=sa; pwd=; database=northwind"

With the DataAdapter in hand, you’re ready to create the DataSet and fill it with the data that you obtain from the SQL select statement:

Dim myDataSet As New DataSet( )
myDataAdapter.Fill(myDataSet, "Customers")

That’s it. You now have a DataSet, and you can query, manipulate, and otherwise manage the data. The DataSet has a collection of tables; you care only about the first one because ...