What are the steps involved to fill a dataset ?

The sample code is shown below:

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

Dim objConn As New SqlConnection(strConnectionString)

objConn.Open()

The First step is to open the connection. Now again note the connection string is loaded from the config file.

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

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

Dim objDataAdapter As New SqlDataAdapter()

objDataAdapter.SelectCommand = objCommand

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

objDataAdapter.Fill(objDataSet)

The 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"

The Fifth step is to bind to the loaded dataset with the GUI. At that moment the sample has a listbox as the UI. The Binding of the UI is completed by using the DefaultView of the dataset. Just to revise each dataset has tables and each table has views. In this sample we have only loaded one table that is Employees table so we are referring that with an index of zero.