A customer reported a issue with creating a Menu ASP.NET Server control included a custom control on DevTrain.de. Every Server Control have method RenderControl which creates the HTML and store it in HTMLtextWriter Object. With that you can create eg HTML Mails which databound content.
In that case the goal is a custom control. On runtime there is a NullReferenceException on renderControl. With other controls like Button or Label this works fine. My first idea was that menu control must interact with the HTTPcontext for eg Rights. But after step into the exceptions I must say its a kind of bug of the menu control. You have to fill property's with values which are filled (i guess) automatically if the control is declerated.
Final solution is
Dim SB As New StringBuilder()
Dim SW As New StringWriter(SB)
Dim o As New HtmlTextWriter(SW)
Dim miMenu As MenuItem = Nothing
Dim menuMenu As System.Web.UI.WebControls.Menu = New System.Web.UI.WebControls.Menu
menuMenu.ID = "menuMenu"
MenuMenu.Orientation = Orientation.Horizontal
menuMenu.MaximumDynamicDisplayLevels = 8
menuMenu.Items.Add(New MenuItem("Home", "eins", "", "eins.aspx"))
miMenu = New MenuItem("Home", "home", "", "Default.aspx")
miMenu.ChildItems.Add(New MenuItem("Home2", "home2", "", "Default.aspx"))
menuMenu.Items.Add(miMenu)
MenuMenu.SkipLinkText = "fake.gif" 'Get_SpacerImageUrl
MenuMenu.StaticPopOutImageUrl = "fake.gif" 'get_PopoutImageUrlInternal
MenuMenu.ScrollUpImageUrl = "fake.gif" 'Get_ScrollUpImageUrlInternal
menuMenu.ScrollDownImageUrl = "fake.gif" 'Get_ScrollDownImageUrlInternal
menuMenu.RenderControl(o)
The graphic file fake.gif does not exist. Its necessary to have a fake value and "" is not possible. The comments shows the internal method shown by the exceptions.