Dim Conn As New SqlConnection("myConnectionString")
Dim Comm As New SqlCommand("SELECT field1 FROM table1", Conn)
Dim reader As SqlReader
 
Try
   Conn.Open()
   reader = Comm.ExecuteQuery()
 
   While reader.Read()
      Combobox1.Items.Add(reader("field1"))
   End While
 
   reader.Close()
   Conn.Close()
Catch ex As Exception
   MessageBox.Show(("Error Occurred: " + ex.Message()))
End Try