AvaloniaUI/Avalonia · error · ArgumentException

Controls for PageSlide must have same parent.

Error message

Controls for PageSlide must have same parent.

What it means

Thrown by TransitioningContentControlPageViewModel.GetVisualParent (ArgumentException) when the two controls' visual parents both exist but are different objects. A PageSlide transition needs both the outgoing and incoming content under the same parent to animate a slide.

Source

Thrown at samples/ControlCatalog/ViewModels/TransitioningContentControlPageViewModel.cs:311

        /// Gets the common visual parent of the two control.
        /// </summary>
        /// <param name="from">The from control.</param>
        /// <param name="to">The to control.</param>
        /// <returns>The common parent.</returns>
        /// <exception cref="ArgumentException">
        /// The two controls do not share a common parent.
        /// </exception>
        /// <remarks>
        /// Any one of the parameters may be null, but not both.
        /// </remarks>
        private static Visual GetVisualParent(Visual? from, Visual? to)
        {
            var p1 = (from ?? to)!.GetVisualParent();
            var p2 = (to ?? from)!.GetVisualParent();

            if (p1 != null && p2 != null && p1 != p2)
            {
                throw new ArgumentException("Controls for PageSlide must have same parent.");
            }

            return p1 ?? throw new InvalidOperationException("Cannot determine visual parent.");
        }
    }
}

View on GitHub (pinned to 11c5427268)

Solutions

1. Host both 'from' and 'to' content in the same parent container.
2. Ensure the TransitioningContentControl owns both visuals before the transition runs.
3. Pass a single non-null argument (the other null) when only one side is available, which skips the parent-mismatch check.

Example fix

// before
var parent = GetVisualParent(from, to); // different parents -> throws

// after
// ensure both share TransitioningContentControl's content host
sameParent.Children.Add(to);
var parent = GetVisualParent(from, to);

var p1 = (from ?? to)?.GetVisualParent();
var p2 = (to ?? from)?.GetVisualParent();
if (p1 != null && p2 != null && p1 != p2) { /* host both under the same parent */ }

static bool SameOrSingleParent(Visual? a, Visual? b) {
  var pa = a?.GetVisualParent(); var pb = b?.GetVisualParent();
  return pa == null || pb == null || pa == pb;
}

try { var p = GetVisualParent(from, to); }
catch (ArgumentException ex) when (ex.Message.Contains("same parent")) { /* reparent and retry */ }

When it happens

Trigger: Calling GetVisualParent(from, to) where p1 = from's parent and p2 = to's parent are both non-null and not equal. The controls are hosted in different containers at transition time.

Common situations: TransitioningContentControl misconfigured with content in separate panels; reparenting during a page change; custom transition hosting that splits the two visuals across panels.

Related errors

• Transition elements have different parents.
• Cannot determine visual parent.
• Device with the corresponding LUID not found
• Not supported format
• Value must be less than 10.

AI-assisted analysis of AvaloniaUI/Avalonia@11c5427268 (2026-08-13). Data as JSON: /api/errors/8eb601499e506fda. Report an issue: GitHub.