Performance issue - Subscribing\Unsubscribing to events

Describe the bug When profiling our test application, we’ve seen that every event subscription takes a noticeable time. In our case, this slows down the application startup for about 200ms.

I made a small sample that shows the issue. I’ve also prepared the WPF test application so you can compare performance.

Steps to reproduce the bug

Steps to reproduce the behavior:

1. Download from the attachments and open the FrameworkEventsTest solution;
2. Set the following solution properties:
   • Configuration - “Release”
   • Platform - “x64”
   • Startup Project - “FrameworkEventsTest (Package)”
3. Run the application
4. Click on the “Click Me” button
5. Wait until the result is shown in the text editor (this may take up to 40 seconds)
6. Repeat steps 4 and 5 for more accurate results

In the table below, you can see the difference between WPF and WinUI performance when subscribing\unsibscribing to the IsEnabledChanged event. I’ve also tried the Loaded and the KeyDown event and got the same results.

Case #	Description	WPF	WinUI pre-2	WinUI pre-3
1	Subscribe to 1 button event with 1 method 1000 times	0	0	0
2	Subscribe and Unsubscribe to 1 button event with 1 method 1000 times	0	26	7
3	Subscribe to 1 button event with 1000 methods 1 time	406	269	341
4	Subscribe and Unsubscribe to 1 button event with 1000 methods 1 time	170	23365	5685
5	Subscribe to 1000 buttons event with 1 method 1 time	0	336	217
6	Subscribe and Unsubscribe to 1000 buttons event with 1 method 1 time	0	326	217

Expected behavior I expect that cases 5 and 6 should be instant (like in WPF) since this is very close to a real scenario: in our app, we have lots of controls with subscriptions to such events as Loaded, Unloaded, IsEnabledChanged, LayoutUpdated.

I’m also surprised at the poor performance of scenario 4; however, I understand that this is synthetic and may not exist in the real application.

Version Info

NuGet package version: [Microsoft.WinUI 3.0.0-preview2.200713.0] [Microsoft.WinUI 3.0.0-preview3.201113.0]

Windows app type:

UWP	Win32
	Yes

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
May 2020 Update (19041)	Yes
November 2019 Update (18363)
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

FrameworkEventsTest.zip

[alexserov]

Hello @chrisglein , I’ve just measured my tests for UWP XAML and WinUI3 (Preview2) for UWP, and here are the results:

Case #	Description	UWP XAML	WinUI for UWP
1	Subscribe to 1 button event with 1 method 1000 times	2	2
2	Subscribe and Unsubscribe to 1 button event with 1 method 1000 times	27	23
3	Subscribe to 1 button event with 1000 methods 1 time	44834	49764
4	Subscribe and Unsubscribe to 1 button event with 1000 methods 1 time	7264	7448
5	Subscribe to 1000 buttons event with 1 method 1 time	5	5
6	Subscribe and Unsubscribe to 1000 buttons event with 1 method 1 time	35	34

The code is the same for every project. You can find it in my attachment to the original post.

As I mentioned earlier, my main interest is in cases 5 and 6 (WinUI for Win32) since we experience the same performance issue in our application.

upd: we have our custom controls in the app; they mostly derive from Microsoft.UI.Xaml.Controls.Control. The ctor looks like follows:

public BaseControl() {
    LayoutUpdated += OnLayoutUpdated;
    Loaded += OnLoaded;
    Unloaded += OnUnloaded;
    IsEnabledChanged += OnIsEnabledChanged;
}

Since we reuse our code from our UWP project, I expect the performance should be the same or even better. Unfortunately, it is not.

[github-actions[bot]]

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