AvaloniaUI/Avalonia · error · InvalidOperationException

There is no server-side counterpart for this object

Error message

There is no server-side counterpart for this object

What it means

Thrown by ICompositorSerializable.TryGetServer when a CompositionObject that reached the commit-batch serialization queue has no server-side counterpart (Server == null). During every commit, Compositor.CommitCore walks its serialization queue (Compositor.cs:138) and asks each object for its server; some types (CompositionAnimation, CompositionPropertySet) are intentionally built with a null server because they serialize via snapshots, so they must never be queued directly.

Source

Thrown at src/Avalonia.Base/Rendering/Composition/CompositionObject.cs:48

        
        /// <summary>
        /// The associated Compositor
        /// </summary>
        public Compositor Compositor { get; }

        SimpleServerObject ICompositorSerializable.TryGetServer(Compositor c)
        {
            Debug.Assert(c == Compositor);
            return Server ?? ThrowInvalidOperation();
        }

        internal SimpleServerObject? Server { get; }
        public bool IsDisposed { get; private set; }
        private bool _registeredForSerialization;

        [MethodImpl(MethodImplOptions.NoInlining)]
        private static SimpleServerObject ThrowInvalidOperation() =>
            throw new InvalidOperationException("There is no server-side counterpart for this object");

        protected internal void Dispose()
        {
            if (!IsDisposed && Server != null)
                Compositor.DisposeOnNextBatch(Server);
            IsDisposed = true;
        }

        /// <summary>
        /// Connects an animation with the specified property of the object and starts the animation.
        /// </summary>
        public void StartAnimation(string propertyName, CompositionAnimation animation)
            => StartAnimation(propertyName, animation, null);
        
        internal virtual void StartAnimation(string propertyName, CompositionAnimation animation, ExpressionVariant? finalValue)
        {
            throw new ArgumentException("Unknown property " + propertyName);
        }

View on GitHub (pinned to 11c5427268)

Solutions

1. Do not register CompositionAnimation / CompositionPropertySet / base CompositionObject instances for serialization yourself; let the Compositor own the queue.
2. Reference PropertySets/animations indirectly via CompositionAnimation.SetReferenceParameter so they serialize through the animation's snapshot path.
3. If you subclass CompositionObject, supply a real SimpleServerObject to the base ctor so Server is non-null.
4. Never reuse a composition object after Dispose(); recreate it from the Compositor.

Example fix

// before
compositor.RegisterForSerialization(myPropertySet); // PropertySet has Server == null

// after
// reference it through an animation instead
anim.SetReferenceParameter("mySet", myPropertySet);

// Only register server-backed objects for serialization; never PropertySets/animations directly.
if (obj is CompositionAnimation || obj is CompositionPropertySet)
    return; // these have no Server and serialize via snapshots
compositor.RegisterForSerialization(obj);

static bool HasServerCounterpart(CompositionObject o) => !o.IsDisposed;

When it happens

Trigger: An object with Server == null (a bare CompositionObject, a CompositionAnimation, or a CompositionPropertySet) is handed to Compositor.RegisterForSerialization and survives to the next CommitCore, so TryGetServer falls into ThrowInvalidOperation.

Common situations: Calling RegisterForSerialization manually on a PropertySet/animation, reusing a composition object across commit boundaries after its server was torn down, or writing a custom CompositionObject subclass that does not pass a server to the base constructor.

Related errors

• The object doesn't have an associated server counterpart
• This resource doesn't exist on that compositor
• {o.GetType()} belongs to a different compositor
• Composition visuals belong to different compositor instances
• Android backend wasn't initialized. Make sure .UseAndroid()

AI-assisted analysis of AvaloniaUI/Avalonia@11c5427268 (2026-08-13). Data as JSON: /api/errors/3297698020c3edbe. Report an issue: GitHub.