Scope, ListBox Population, Headaches

I just spent oh, 5 hours or so tracking down the cause of the following problem:
Populating a vb.net 2005 listbox with Person objects, the listbox appeared correctly, but when I tried to manipulate (use SelectedItem) the list later, SelectedItem could return only the last entry.
What I finally learned is that the routine I used to fill the listbox with had a problem with variable scope.
I dimensioned the Person instance once and tried to use it for every new Person. When I moved the dimension to inside the While ... End While block, the behavior of the listbox became as expected. Ugh. Glad to be through that. I Hope this helps someone down the road.
Here is the code that works. Of particular interest is the location of the line
"Dim prsn as New Oxalis.Person"

Private Sub fill_existing_staff()
        'fill the staff and task listboxes with any previously inserted values
        'lookup the projectstaff table
        Dim cmd As SqlCommand = New SqlCommand("spProjectStaff")
        cmd.CommandType = CommandType.StoredProcedure
        Dim con As New SqlConnection(m_SQLConn)

        con.Open()
        'filter on the selected ProjectID
        cmd.Parameters.AddWithValue("@ProjectID", Me.TreeView1.SelectedNode.Tag.ToString)
        cmd.Connection = con
        'Clear any previous entries
        Me.StaffIDListBox.Items.Clear()
        'return the current values
        Dim dtr As SqlDataReader = cmd.ExecuteReader()
        'read them into the listbox
        While dtr.Read()
            Dim prsn As New Oxalis.Person
            prsn.PersonID = dtr.Item(0)
            prsn.Name = dtr.Item(1)
           
            Me.StaffIDListBox.Items.Add(prsn)
            Debug.Print("Person added: " & prsn.Name)
        End While
        dtr.Close()
    End Sub