[C# Markup] Enhancement request: Extension methods for adding event handlers

[baskren]

I'm in the process of migration from my home-brewed C# markup to Uno's C# markup. 99% of my home-brew version is redundant (or inferior) to Uno's C# markup. However, there is a small feature (that I use a lot) that I'd like to see if it would make sense to add to Uno's markup: adding event handlers. I've used ButtonBase.Click as an example, below.

sample usage:

    var x = new Button().AddClickHandler((s,e) => Console.WriteLine("Clicked")).AddClickHandler(OnClicked);

Yes, the code's pretty simple:

    public static TElement AddClickHandler<TElement>(this TElement element, RoutedEventHandler handler) where TElement : ElementType
    { element.Click += handler; return element; }

I thought this might be a good first "pull request" for me but I failed to find the code base for Uno's C# markup in the public repos.

[francoistanguay]

Hi,

The repo is here: https://github.com/unoplatform/uno.csharpmarkup

This is something we had discussed but preferred not to implement for now as it's relatively easy to add in your app as an extension method but most importantly, it is extremely prone to memory leaks as you're not ever unsubscribing from the handlers.

More info here: https://github.com/unoplatform/uno.csharpmarkup/issues/93

[baskren]

100% in agreement with you about the risk of memory leaks.

FWIW: both links shared are for private repos.

[francoistanguay]

My bad. This was the issue/discussion we had internally:

One other downside of this is that it adds to the API surface and as there might be quite a few events, we're always being careful about Roslyn performance. We had to reduce API surface to get decent Intellisense performance.

So all in all, not something we've prioritized at this point but could revisit in the future. Hopefully in the meantime you can add those frequently used event wrappers to your own app.

[baskren]

No worries, Francois. And yes, I have my own home brew version that does as you suggest.