ViewComponent and @Section

[grahamehorner]

The @section scripts don't render in a ViewComponent, view component should have the ability to include scripts within the @section unlike partital views as components may be reused across many views and the component is responsible for it's own functionality.

[Eilon]

@grahamehorner can you explain a bit more what scenario you have? Does the ViewComponent have its own layout page and view, and an @section for scripts? Or is the ViewComponent trying to have an @section for scripts for the calling view's layout page?

[grahamehorner]

I have the need to use a view component that has a view component layout and uses a view model; the layout includes a @section for scripts; at present the view component layout is rendering but fails to include the @section script at the end of the rendered page/output; this results in the view component not having the required functionality when rendered to the client.

[grahamehorner]

I have forked the code and updated the default.cshtml in the Views\Shared\Components\Tags folder to show what I believe to be an issue; as the @section scripts fails to render in the pages that make use of the ViewComponent.

[grahamehorner]

please see https://github.com/grahamehorner/Mvc

[dougbu]

@grahamehorner nothing shows up as changed in that forked repo. What branches should we compare?

Might work better to post a standalone example.

[grahamehorner]

@dougbu apologies the sync failed and I had not realised; the simple update should now be invisble

[dougbu]

@grahamehorner thanks I've confirmed the behaviour you've described. The ViewViewComponentResult for Default.cshtml executes independently of the main ViewResult and its Layout value is null by default. Without a layout, no sections are rendered. The same behaviour occurs in display or editor templates and partial views.

The most obvious issue here is views which have Layout == null and contain @section do not encounter InvalidOperationExceptions because the section is not rendered. Such an Exception would have caught the oddly-placed / unrendered section up front.

The remainder appears to be By Design...

If you added a layout for your view component, it could render the "scripts" section. Rendering should be conditional in your scenario because view components should be independent enough to be used multiple times in the same page. But that condition correctly leads to errors because layouts confirm all defined sections are rendered.

With respect to defining a section in a view component that the main page's layout renders, note view components (and partials and templates...) should work in any page. Defining a section in any of these views with the expectation its name is known to the page or page layout creates an unnatural coupling.

[grahamehorner]

why would a View or a ViewComponent ever have a Layout of null? unless explicitly set? shouldn't they inherit from the _ViewStart.cshtml layout or the layout of the parent/hosting cshtml?

I understand the 'unnatural coupling' comment and agree; but how could we achieve the following:-
a view component that requires some scripts for it's functionality (following best practice) needs to inject javascript at a given location (the end of the rendered html but prior to the closing body tag) but only when the ViewComponent is including in the View rendering ;)

[grahamehorner]

or should the ViewComponent be able to be supplied a options object for the View where it can then use this to inject style/script/html or hook into dom elements of the View ?