[Blazor] Optional constraint to component nesting (UI warning/Compilation error)

[rafaelchampion]

In DevExpress they have a nice touch to their components where:

• Sub-components may only be nested within a specific parent component
• A parent component may only nest a defined list of components

This is shown as an UI warning much like when you try to nest a 'div' inside an 'ul'.

E.g.:

In the ASPxGridView component, Columns is a valid nestable child component:

<dx:ASPxGridView runat="server">
      <Columns></Columns>
</dx:ASPxGridView>

In comparison, if we try to nest an Items component (nestable within other components like ASPxComboBox, but not within ASPxGridView) or any other component/tag, like this:

<dx:ASPxGridView runat="server">
        <Items></Items>
</dx:ASPxGridView>

The UI displays a warning: Element 'Items' not supported.

Similarly, it's not possible to use a standalone Columns component outside an ASPxGridView component.

It would be nice to be able to:

• Declare a specific list of components to be nestable inside a parent component
  and/or
• Specify that a component may only be usable if nested inside a specific component/list of components

This allows a child component to only be used where it's strictly intended to be used, like if you have events that require a determined component tree to work and also creates a failproof use of a determined component.

For example if I have a card-list component and a card-list-item component with a delete button and I want the card-list-item component to be strictly nestable inside a card-list component so when I click the delete button an event is always fired in the parent component.

I know it's not an ultra required feature but it would be nice to have.

[javiercn]

@rafaelchampion thanks for contacting us.

This is a duplicate issue of #12302. Closing this issue in favor of that one, please go ahead and up-vote that issue instead to help us track progress.