Templated XAML controls for WinUI 3 C#

[get-flat]

Describe the bug

Exception on InitializeComponent:
Exception thrown at 0x75A246D2 in BgLabelControlApp.exe: Microsoft C++ exception: winrt::hresult_error at memory location 0x02DBDE68.

Steps to reproduce the bug

Steps to reproduce the behavior:

1. Follow instructions: https://docs.microsoft.com/en-us/windows/apps/winui/winui3/xaml-templated-controls-csharp-winui-3

Expected behavior

No crash
Update documentation to provide working example

Screenshots

Version Info

Version 16.9.0 Preview 2.0 (vanilla C# only installation - https://docs.microsoft.com/en-us/windows/apps/winui/winui3/)

NuGet package version:
[Microsoft.WinUI 3.0.0-preview3.201113.0]

Windows app type:

UWP	Win32
No	Yes

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
May 2020 Update (19041)
November 2019 Update (18363)	Yes
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Xbox
Surface Hub
IoT

Additional context

Please fix documentation: Generic.xaml is autogenerated when new CustomControl is added.
Please update documentation: "Name the new control "BgLabelControl" and click Add. This will add two new files to your project. BgLabelControl.cs contains the code-behind for the control." What should be the other file? Only .cs file is created.

[get-flat]

May be duplicate of: #3657
Could you please update documentation that even for the most basic examples from your documentation you have to apply hacky workarounds.

[StephenLPeters]

@get-flat are you testing on preview 2 or 3? The version info states both :)

[ghost]

This issue has been automatically marked as stale because it has been marked as requiring author feedback but has not had any activity for 7 days. It will be closed if no further activity occurs within 7 days of this comment.

[get-flat]

@StephenLPeters I'm using version [Microsoft.WinUI 3.0.0-preview3.201113.0]
(16.9.0 Preview 2.0, I mean Preview 2 of Visual Studio version 16.9.0. I wasn't sure if VS ver is relevant)

[StephenLPeters]

@evelynwu-msft FYI

[evelynwu-msft]

@get-flat Thanks for your report! The exception you're seeing is known and non-fatal; execution can be safely continued past it. Alternatively, if you find it too noisy, you can disable the winrt::check_hresult exception in Visual Studio's Exception Settings window.

I'll talk to our writer and see about getting the sample documentation updated to correct the errors you identified.

[drewbatgit]

The sample documentation has been updated to note that:

1. BgLabelControl.cs is the only file generated when you add Custom Control to the project
2. Generic.xaml is automatically generated when you add the control, so you don't need to manual create it, just update the contents.

[Herdubreid]

The good news is that I don't get an Exception, the downside however is that I can't get this to work at all.

Also, isn't there something missing for this handler to be called? (I assume the curly bracket repeat is just a typo):

private static void OnLabelChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    {
        BgLabelControl labelControl = d as BgLabelControl; //null checks omitted
        String s = e.NewValue as String; //null checks omitted
        if (s == String.Empty)
        {
            labelControl.HasLabelValue = false;
        }
        else
        {
            labelControl.HasLabelValue = true;
        }
    }
}

My project:
https://github.com/Herdubreid/BgLabelControlApp

[drewbatgit]

Thanks for catching this. In order for the changed handler to be invoked you have to register the callback:

DependencyProperty LabelProperty = DependencyProperty.Register(
            nameof(Label), 
            typeof(string),
            typeof(BgLabelControl), 
            new PropertyMetadata(default(string), new PropertyChangedCallback(OnLabelChanged)));

The article has been updated with this change (and the superfluous brackets have been removed). Thanks again!

[Herdubreid]

Thanks for clearing that up @drewbatgit

I can successfully set a breakpoint on the handler, so the property is definitely updated.
I can't however get it to show up.

You can check my code here: https://github.com/Herdubreid/BgLabelControlApp