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Been dealing with a casting exception during design time only that getting me nuts.

I'm trying to create a custom control for winRT (a week view control just like windows phone 8.1). The control works fine during run time but in design time it gives me COMException. During my investigation of the cause of this COMException, I found out that there is a casting exception inside one of the component of my control. This component is a custom listview that implement ContainerContentChanging event. Inside this event there is a casting which raises this exception.

Here is a the custom list view class:-

The code is removed coz the source code is shared below.

The TemplatedListViewEntry cctor look like this one:-

The code is removed coz the source code is shared below.

And the AppointmentModel:-

The code is removed coz the source code is shared below.

OBS!!! while debugging using 2 instance of VS or VS+Blend and put a breakpoint before this line I can see that args.Item is of type ContentControl while during run time it is AppointmentModel.

Could it be a problem with the ItemsSource which is null at design time?

If yes how should I preceed and assign this_ If No, anyone here that can help me figure out what is the problem?

OBS!!! I anyone needs more info please ask and I would gladly share the entire code with you.

Edit 1 Even if i initiate my viewmodel in the cctor of the custom Control, it raises casting exception in Designtime and not in Run tim

Edit 2 After i wrote Edit 1 above i noticed that now i have to Cast exception in two different Styles (CustomWeekView style and TemplatedListView Style) this is if you open Generic.xaml inside Blend. It is really getting annoying and i'm out of thoughts now. That is why i decided to share the source code of this Project, hopfully someone will be able to help looking at it. Below you will see the source code. CustomWeekView

DreamNet
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  • If you want to populate a list at design time then you can use "DesignTime Data": http://msdn.microsoft.com/en-us/magazine/dn169081.aspx , I use it to preview a lot DataTemplates inside my test Apps at design time. – Chubosaurus Software Nov 03 '14 at 05:46
  • @ChubosaurusSoftware i'm totally aware of that when it it comes to usual apps. My problem is during the process of creating a custom control, ie. the dll that can be used in another app, and I don't know where to use DesignTime Data in such a process. Anyway thanks for your help. – DreamNet Nov 03 '14 at 08:19
  • so using ` – Chubosaurus Software Nov 03 '14 at 08:29
  • @ChubosaurusSoftware can you use that in Style? coz im only defining TemplatedListView as default style. – DreamNet Nov 03 '14 at 08:58
  • Check this out. Maybe it will help. http://stackoverflow.com/questions/26500991/visual-studio-designer-crashes-when-overrideing-wndproc – Russell Trahan Nov 12 '14 at 05:00

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