stack panel children

Guys I have external data which is saved on .Txt file; I want to load each text in that .txt file to the stack panel children when form load event.

simply, I want to add .txt information to stack panel when form is load, like read .txt file on regular Listbox .

so is it possible to do that ?. I have following command with me.

Private Sub MainWindow_Loaded(ByVal sender As Object, ByVal e As System.Windows.RoutedEventArgs) Handles Me.Loaded

    Dim r As New IO.StreamReader("D:\save\test.text")
    While (r.Peek() > -1)
        ListBox1.Items.Add(st)  '' where st is a stack panel


    End While

unfortunately in form load event Stack panel not add to program window because i already created the Dynamic stack panel add event .

can you guys help me please.