Blazor: add support for beforetoggle event

[chucker]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

I am trying to use onbeforetoggle to manipulate an element before it appears.

Describe the solution you'd like

Support onbeforetoggle. The event type is ToggleEvent, which we already have.

Additional context

The larger goal here was to use https://developer.mozilla.org/en-US/docs/Web/API/Popover_API.

[javiercn]

@chucker thanks for contacting us.

You can already do this yourself by using a custom event handler as described https://learn.microsoft.com/en-us/aspnet/core/blazor/components/event-handling?view=aspnetcore-8.0#general-configuration

Note that there are things that due to Blazor's nature will not be possible to do (like modifying the HTML element using C# before the event applies, as that would require everything to run synchronously, which is not guaranteed and not something we are willing to depend on).

[ghost]

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[xcaptain]

@javiercn Hello, I'm also trying the new popover api on blazor wasm, I have a similar problem, I don't need to listen to the beforetoggle event, I want to know how to call the hidePopover method of the popover dom element. For example, I want to hide the popover after I clicked the dropdown items.

Mozilla doc: https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/hidePopover