What are the steps involved to fill a dataset? OR How can we use data adapter to fill a dataset?

 Posted by ArticlesMaint on 9/17/2009 | Category: ADO.NET Interview questions | Views: 5262


Answer: -
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 List Box. 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 data adapter.


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



Fifth step is to bind to the loaded dataset with the GUI. At this moment sample has list box as the UI. Binding of the UI is done by using Default View 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.
Just say all the five steps during interview and you will see the smile on the interviewer’s face and appointment letter in your hand.


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