First of all its quite strange that you dont have unique values column (primary key) in your table. You should have one, otherwise its not a good system design.
Change your query to this
Dim myadapter As New SqlDataAdapter("SELECT DISTINCT ID FROM PatOrder (NOLOCK) ", conMod.Con)
and then bind appropriate column with your list box
ListPatient.DisplayMember = "ID"
This will also solve your problem, and much better than using