retrieving data from SQL in VB (part 2) - vb.net

Question

I am trying to populate a listbox by retrieving data from a database through sql. I have asked this question earlier but i was using a different configuration and the one i'm using now isn't giving any results.
retrieving data in VB from SQL
That is my old post. I will now provide the code to the newer version of my attempt.
Imports System.Data.Sql
Imports System.Data.SqlClient
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim conn As New SqlConnection
conn.Open()
Dim comm As New SqlCommand("SELECT name FROM Table_1", conn)
Dim reader As SqlDataReader = comm.ExecuteReader
Dim dt As New DataTable
dt.Load(reader)
ListBox1.Items.Add(dt)
End Sub
End Class
If anyone would be willing to help me out i'd greatly appreciate it. If possible, use a practical approach when trying to enlighten me, as that works best.
edit 1
Imports System.Data.Sql
Imports System.Data.SqlClient
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim connString As String = "Data Source=THE_SHOGUNATE\SQLEXPRESS;Initial Catalog=le_database;Integrated Security=True"
Dim conn As New SqlConnection(connString)
conn.Open()
Dim comm As New SqlCommand("SELECT name FROM Table_1", conn)
Dim reader As SqlDataReader = comm.ExecuteReader
Dim dt As New DataTable
dt.Load(reader)
ListBox1.DataSource = dt
End Sub
End Class
With this code the listbox populates with 6 instances of "System.Data.DataRowView" strings, 6 being the number of items in my table. How do i get the actual values?

Answer 1

You missed the connectionString
If you want to populate list from DB there are many ways
With DataReader
Imports System.Data.Sql
Imports System.Data.SqlClient
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim connectionString As String = "Data Sourec=localhost;........."
Dim conn As New SqlConnection(connectionString)
conn.Open()
Dim comm As New SqlCommand("SELECT name FROM Table_1", conn)
Dim reader As SqlDataReader = comm.ExecuteReader
/* As it is not working i commented this
listBox1.ItemsSource = dt; // use this instead of ListBox1.Items.Add(dt)
//because Add event add only one item in the list.
*/
Dim i As Integer
i=0
while reader.read()
listbox1.Items.Add(dr(i).ToString);
i++
End While
End Sub
End Class
With DataTable
Imports System.Data.Sql
Imports System.Data.SqlClient
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim connectionString As String = "Data Sourec=localhost;........."
Dim conn As New SqlConnection(connectionString)
conn.Open()
// Create new DataAdapter
SqlDataAdapter a = new SqlDataAdapter("SELECT * FROM EmployeeIDs", c)
// Use DataAdapter to fill DataTable
DataTable dt = new DataTable();
a.Fill(dt);
ListBox1.DataSource = dt;
ListBox1.DataTextField = "name";
End Sub
End Class
EDIT:
Other parameters of connection string depends on your security and all that. You must see this link Connection strings for SQL Server 2008

Answer 2

Set the DisplayMember property after DataSource binding:
ListBox1.DataSource = dt
ListBox1.DisplayMember="name"

Answer 3

The last solution I saw should work, but there are a couple important best practices to keep in mind regarding SQL Server.
1) Avoid Select * whenever possible, instead name your columns explicitly. Select * causes SQL to perform extra work if you do not intend to pull down all the columns in the table. It's also not future-proof, since a dba could add a VARBINARY(MAX) column in the future, and populate it with gigs worth of blob data, This scenario would make your query as written slow down substantially and unnecessarily.
2) Always remember to close your SQLConnection when you're done with it. This will free up a SQL connection and resources.
if (cn.State != ConnectionState.Closed)
cn.Close();
Another cool trick is to use the USING directive which will dispose of the SqlConnection object when execution passes out of scope.
using (SqlConnection cn = new SqlConnection(sConnectionString))
{
if (cn.State != ConnectionState.Open)
cn.Open();
// add query code here.
if (cn.State != ConnectionState.Closed)
cn.Close();
}
don't forget to close your SqlDataReader after the read loop is complete.
if (!dr.IsClosed)
dr.Close();
I hope this helps.
Andre Ranieri