dotnet/maui · error · ArgumentNullException

public ElementEventArgs(Element element) => Element = elemen

Error message

public ElementEventArgs(Element element) => Element = element ?? throw new ArgumentNullException(nameof(element));

What it means

Thrown by the ElementEventArgs constructor when the element argument is null. ElementEventArgs wraps a single Element for events like ChildAdded, ChildRemoved, DescendantAdded, DescendantRemoved. The constructor rejects null so event consumers can always rely on the Element property being non-null.

Source

Thrown at src/Controls/src/Core/Element/ElementEventArgs.cs:11

#nullable disable
using System;

namespace Microsoft.Maui.Controls
{
	/// <summary>Provides data for events pertaining to a single <see cref="Microsoft.Maui.Controls.Element"/>.</summary>
	public class ElementEventArgs : EventArgs
	{
		/// <summary>Constructs and initializes a new instance of the <see cref="Microsoft.Maui.Controls.ElementEventArgs"/> class.</summary>
		/// <param name="element">The element relevant to the event.</param>
		public ElementEventArgs(Element element) => Element = element ?? throw new ArgumentNullException(nameof(element));
	}
}

View on GitHub (pinned to f377ff1c5e)

Solutions

1. Pass a non-null Element when constructing ElementEventArgs.
2. If raising events in cleanup code, null-check the element before constructing the args.
3. Subscribe to ChildAdded/Removed etc. via the framework rather than constructing args manually.

Example fix

// before
ChildAdded?.Invoke(this, new ElementEventArgs(null)); // throws
// after
if (child != null)
    ChildAdded?.Invoke(this, new ElementEventArgs(child));

if (element == null) throw new ArgumentNullException(nameof(element));
var args = new ElementEventArgs(element);

try { ChildAdded?.Invoke(this, new ElementEventArgs(child)); }
catch (ArgumentNullException) { /* child was null; skip raising */ }

When it happens

Trigger: Constructing new ElementEventArgs(null) directly, or framework/internal code raising child/descendant events with a null element reference (e.g., during cleanup when an element was already nulled out).

Common situations: Custom code or third-party libraries manually raising ChildAdded/ChildRemoved/DescendantAdded/DescendantRemoved events with null; element lifecycle bugs where an event is raised after the element reference was cleared.

Related errors

• _ = view ?? throw new ArgumentNullException(nameof(view));
• throw new ArgumentNullException(nameof(type));
• internal ElementTemplate(Func<object> loadTemplate) : this()
• No test assembly found.
• Unable to find the required services. Please add all the req

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/913892b496611f35. Report an issue: GitHub.