Split Controls: InAppNotification smaple throws execption.

[Rosuavio]

Describe the bug

When opening the InAppNotification sample, the sample app throws an exception.

Microsoft.Toolkit.Uwp.SampleApp.exe!Microsoft.Toolkit.Uwp.SampleApp.SampleController.OnNavigatedTo(Windows.UI.Xaml.Navigation.NavigationEventArgs e) Line 232 C#

System.NotSupportedException
  HResult=0x80131515
  Message=Unrecognized short identifier 'StackMode'; Define type and parameters of property in first occurrence in InAppNotificationXaml.bind.
  Source=Microsoft.Toolkit.Uwp.SampleApp
  StackTrace:
   at Microsoft.Toolkit.Uwp.SampleApp.Sample.<PreparePropertyDescriptorAsync>d__91.MoveNext() in C:\Users\Rosario\source\repos\WindowsCommunityToolkit\Microsoft.Toolkit.Uwp.SampleApp\Models\Sample.cs:line 466
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at Microsoft.Toolkit.Uwp.SampleApp.SampleController.<OnNavigatedTo>d__14.MoveNext() in C:\Users\Rosario\source\repos\WindowsCommunityToolkit\Microsoft.Toolkit.Uwp.SampleApp\Pages\SampleController.xaml.cs:line 232

  This exception was originally thrown at this call stack:
    Microsoft.Toolkit.Uwp.SampleApp.Sample.PreparePropertyDescriptorAsync() in Sample.cs
    [External Code]
    Microsoft.Toolkit.Uwp.SampleApp.SampleController.OnNavigatedTo(Windows.UI.Xaml.Navigation.NavigationEventArgs) in SampleController.xaml.cs

• Is this bug a regression in the toolkit? If so, what toolkit version did you last see it work: dev/split-controls

Steps to Reproduce

• Can this be reproduced in the Sample App? (Either in a sample as-is or with new XAML pasted in the editor.) If so, please provide custom XAML or steps to reproduce. If not, let us know why it can't be reproduced (e.g. more complex setup, environment, dependencies, etc...)

Steps to reproduce the behavior:

1. Open InAppNotification sample in sample app
2. Exception gets thrown

Expected behavior

A clear and concise description of what you expected to happen.

Screenshots

If applicable, add screenshots to help explain your problem.

Environment

NuGet Package(s): 

Package Version(s): 

Windows 10 Build Number:
- [ ] Fall Creators Update (16299)
- [ ] April 2018 Update (17134)
- [ ] October 2018 Update (17763)
- [ ] May 2019 Update (18362)
- [ ] May 2020 Update (19041)
- [ ] Insider Build (build number: )

App min and target version:
- [ ] Fall Creators Update (16299)
- [ ] April 2018 Update (17134)
- [ ] October 2018 Update (17763)
- [ ] May 2019 Update (18362)
- [ ] May 2020 Update (19041)
- [ ] Insider Build (xxxxx)

Device form factor:
- [ ] Desktop
- [ ] Xbox
- [ ] Surface Hub
- [ ] IoT

Visual Studio 
- [ ] 2017 (version: )
- [ ] 2019 (version: ) 
- [ ] 2019 Preview (version: )

Additional context

Add any other context about the problem here.

Hello RosarioPulella, thank you for opening an issue with us!

I have automatically added a "needs triage" label to help get things started. Our team will analyze and investigate the issue, and escalate it to the relevant team if possible. Other community members may also look into the issue and provide feedback 🙌

[Rosuavio]

This is due to the LookForTypeByName (Microsoft.Toolkit.Uwp.SampleApp\Models\Sample.cs 629 29) fn not loading types in the assembly containing InAppNotification (Controls.Core). Working on a fix.