What are the steps involved to fill a dataset ?

Sample code is provided in “WindowsDataSetSample” folder in CD.”LoadData” has all the implementation of connecting and loading to dataset. This dataset is finally bind to a ListBox. Below is the sample code.

Private Sub LoadData()
Dim strConnectionString As String
strConnectionString = AppSettings.Item(“ConnectionString”)
Dim objConn As New SqlConnection(strConnectionString)
objConn.Open()
Dim objCommand As New SqlCommand(“Select FirstName from
Employees”)
objCommand.Connection = objConn
Dim objDataAdapter As New SqlDataAdapter()
objDataAdapter.SelectCommand = objCommand
Dim objDataSet As New DataSet
End Sub

In such type of questions interviewer is looking from practical angle, that have you worked with dataset and datadapters. Let me try to explain the above code first and then we move to what steps should be told during interview.

Dim objConn As New SqlConnection(strConnectionString)
objConn.Open()

First step is to open the connection.Again note the connection string is loaded from config file.

Dim objCommand As New SqlCommand(“Select FirstName from Employees”)
objCommand.Connection = objConn

Second step is to create a command object with appropriate SQL and set the connection object to this command.

Dim objDataAdapter As New SqlDataAdapter()
objDataAdapter.SelectCommand = objCommand

Third steps is to create the Adapter object and pass the command object to the adapter object.

objDataAdapter.Fill(objDataSet)

Fourth step is to load the dataset using the “Fill” method of the dataadapter.

lstData.DataSource = objDataSet.Tables(0).DefaultView
lstData.DisplayMember = “FirstName”
lstData.ValueMember = “FirstName”

listbox as the UI. Binding of the UI is done by using DefaultView of the dataset. Just to revise every dataset has tables and every table has views. In this sample we have only loaded one table i.e. Employees table so we are referring that with an index of zero.