searching the list box

In a button click I will make apanel visible inside that Panel I have textbox, listbox with data(Data already populated from the stored procedure) 
Now What I am trying to do is If i type some thing in the text box like 'kris' all the items that matches 'kris' should get selected in the list box.
Please see my code below
Protected Sub TextBox1_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        Dim dr As SqlDataReader
        dr = SearchUsers(TextBox1.Text)
    End Sub
 
right now dr is bringing all the matched rows and I am not sure how can I make the listbox to select all the retrieved rows
.aspx
<asp:listbox id="ListUsers" runat="server" DataValueField="UserID" DataTextField="Name" SelectionMode ...