stride3d/stride · error · ArgumentNullException

Value cannot be null. (Parameter 'e')

Error message

Value cannot be null. (Parameter 'e')

What it means

Argument-null validation in UIElement.RaiseEvent: the RoutedEventArgs e is null. RaiseEvent identifies which RoutedEvent to raise from the event data carried in e; without it nothing can be routed, so it throws ArgumentNullException named 'e', exactly as the method's <exception> documentation declares. All the RaiseTouch*/RaiseKeyPressed helpers pass constructed event args, so this fires when user code calls RaiseEvent with null.

Solutions

1. Pass a non-null RoutedEventArgs (or a derived type matching the RoutedEvent) to RaiseEvent.
2. Construct the event args at the call site — e.g. in RaiseTouchDownEvent/RaiseKeyPressedEvent helpers — before raising, and never forward a null args reference.
3. Guard call sites where event args come from an external source (input pipeline, pooling) and may be null.

When it happens

Trigger: Thrown at sources/engine/Stride.UI/UIElement.Events.cs:165 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/f516b54da9526210. Report an issue: GitHub.

Appendix: source

Thrown at sources/engine/Stride.UI/UIElement.Events.cs:165

                RoutedEventHandlerInfoListPool.Enqueue(pooledList);
            }

            // propagate afterwards if bubbling
            if (routedEvent.RoutingStrategy == RoutingStrategy.Bubble)
                VisualParent?.PropagateRoutedEvent(e);
        }

        /// <summary>
        /// Raises a specific routed event. The <see cref="RoutedEvent"/> to be raised is identified within the <see cref="RoutedEventArgs"/> instance 
        /// that is provided (as the <see cref="RoutedEvent"/> property of that event data).
        /// </summary>
        /// <param name="e">A <see cref="RoutedEventArgs"/> that contains the event data and also identifies the event to raise.</param>
        /// <exception cref="ArgumentNullException"><paramref name="e"/> is null.</exception>
        /// <exception cref="InvalidOperationException">The type of the routed event argument <paramref name="e"/> does not match the event handler second argument type.</exception>
        public void RaiseEvent(RoutedEventArgs e)
        {
            if (e == null)
                throw new ArgumentNullException(nameof(e));

            if (e.RoutedEvent == null)
                return;

            if (!e.RoutedEvent.HandlerSecondArgumentType.GetTypeInfo().IsAssignableFrom(e.GetType().GetTypeInfo()))
                throw new InvalidOperationException("The type of second parameter of the handler (" + e.RoutedEvent.HandlerSecondArgumentType
                                                    + ") is not assignable from the parameter 'e' type (" + e.GetType() + ").");

            var sourceWasNull = e.Source == null;
            if (sourceWasNull) // set the source to default if needed
                e.Source = this;

            e.StartEventRouting();

            PropagateRoutedEvent(e);

            e.EndEventRouting();

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