[MVUX] Retry in FeedView.ErrorTemplate is a silently dead button: {Binding Refresh} resolves against the Exception

[mtmattei]

Current behavior

Inside FeedView.ErrorTemplate, the DataContext is the thrown Exception, not the FeedViewState. So the natural way to wire a Retry button:

<mvux:FeedView Source="{Binding Products}">
  <mvux:FeedView.ErrorTemplate>
    <DataTemplate>
      <Button Content="Retry" Command="{Binding Refresh}" />
    </DataTemplate>
  </mvux:FeedView.ErrorTemplate>
</mvux:FeedView>

...binds Command to nothing. The button still renders enabled, still exposes an invoke pattern to automation, and does nothing at all when clicked. {Binding Parent.X} fails there for the same reason, since Parent also lives on FeedViewState.

The reason this is worth reporting rather than just documenting: every cheap verification passes. The build succeeds, there is no binding-failure symptom at the usual severity, the button looks correct in a screenshot, and the same {Binding Refresh} expression is valid inside ValueTemplate — so it survives code review by pattern-matching against working code. The only way to discover it is to click the button with a healthy data source and notice nothing happened.

I confirmed the cause at runtime by inspecting the button's DataContext in a running app: it serialises as System.InvalidOperationException (the exception the feed threw), with no Refresh member anywhere on it.

Expected behavior

Either:

1. Refresh (and ideally FeedViewState) is reachable from ErrorTemplate's DataContext, so the obvious binding works; or
2. the failed binding surfaces loudly — a binding error at a visible severity, or an analyser warning on {Binding Refresh} inside an ErrorTemplate; or
3. at minimum, the docs for FeedView error handling show the ElementName form explicitly, since the obvious form is a silent no-op.

Workaround

Name the FeedView and bind through ElementName, which resolves correctly even from inside a nested ContentTemplate:

<mvux:FeedView x:Name="ProductsFeed" Source="{Binding Products}">
  <mvux:FeedView.ErrorTemplate>
    <DataTemplate>
      <Button Content="Retry" Command="{Binding Refresh, ElementName=ProductsFeed}" />
    </DataTemplate>
  </mvux:FeedView.ErrorTemplate>
</mvux:FeedView>

How to reproduce it

1. Expose an IFeed<T> / IListFeed<T> whose service throws.
2. Bind a FeedView to it with an ErrorTemplate containing <Button Command="{Binding Refresh}" />.
3. Run, let it fail into the error state, then make the data source healthy while the app is still running and click Retry — the service is never called again.
4. Swap in the ElementName form and repeat — the service is called and the feed recovers.

Environment

• Uno.Sdk 6.7.0-dev.105 and 6.8.0-dev.12 (same behaviour on both)
• net10.0-desktop
• Windows 11, .NET 10.0.303