EventCallback vs Func

[Chryssie]

There's a lot of component [Parameter]s that use Func<Task> or Func<T, Task> instead of EventCallback or EventCallback<T> and I was wondering if there was any specific reason that is the case. Using EventCallback or EventCallback<T> will call Task IHandleEvent.HandleEventAsync(EventCallbackWorkItem callback, object? arg) which for Microsoft.AspNetCore.Components.ComponentBase will automatically call StateHasChanged() on the handling component after the callback is executed which is, typically, the expected behaviour.

If callers do not want this behaviour they are able to bypass it by constructing their own EventCallback instance by using one of the EventCallback.Factory.Create methods with a non-null receiver (that is something other than the component) and a callback that does not have a .Target of the component (ie: it's not a closure of an instance method). However, this should not be required in most scenarios where either:

1. The caller cannot or does not wish to implement ShouldRender() (or any equivalent construct for components that don't inherit from Microsoft.AspNetCore.Components.ComponentBase).
2. -AND- Either:
   1. Calling StateHasChanged() causes an infinite loop of event invocations. However, this would mostly be indicative of a bug where the setting of value by the parent component triggers a change notification of the child component for the same thing (or something that will trigger a change of the thing originally set by the parent.
   2. Calling StateHasChanged() this frequently causes a significant performance impact.
   3. Calling StateHasChanged() at that particular time has undesirable side-effects.