ASP.net Error adding control in Page PreInit event

Hi. The following code gives me an error at the line marked "Error Here"

    Private Sub Dynamic_Data_PreInit(sender As Object, e As EventArgs) Handles Me.PreInit
        Dim oDropDownList As New DropDownList
        oDropDownList.ID = "d1"
        oDropDownList.Items.Add("Test")
        Me.Panel_Controls.Controls.Add(oDropDownList) 'Error here
  End Sub