dotnet/maui · error · ArgumentException

Element is not of type CheckBox

Error message

Element is not of type CheckBox

What it means

Thrown by CheckBoxRendererBase.SetElement when the VisualElement passed to the renderer is not a CheckBox. The AppCompat renderer for CheckBox is hard-bound to the CheckBox controls type; any other element type is a registration or wiring mistake. The guard runs before any property subscription so the renderer never enters an invalid state.

Source

Thrown at src/Compatibility/Core/src/Android/AppCompat/CheckBoxRendererBase.cs:107

		{
			if (_disposed)
			{
				return new SizeRequest();
			}
			Measure(widthConstraint, heightConstraint);
			return new SizeRequest(new Size(MeasuredWidth, MeasuredHeight), MinimumSize());
		}

		void IVisualElementRenderer.SetElement(VisualElement element)
		{
			if (element == null)
			{
				throw new ArgumentNullException(nameof(element));
			}

			if (!(element is CheckBox checkBox))
			{
				throw new ArgumentException("Element is not of type " + typeof(CheckBox), nameof(element));
			}

			CheckBox oldElement = Element;
			Element = checkBox;

			Performance.Start(out string reference);

			if (oldElement != null)
			{
				oldElement.PropertyChanged -= OnElementPropertyChanged;
			}

			element.PropertyChanged += OnElementPropertyChanged;

			if (_tracker == null)
			{
				_tracker = new VisualElementTracker(this);
			}

View on GitHub (pinned to f377ff1c5e)

Solutions

1. Verify the ExportRenderer/ handler registration maps CheckBox (and only CheckBox) to CheckBoxRendererBase-derived types.
2. Check that the element passed to the renderer is actually a CheckBox instance and not a subclass of a different control.
3. If you need a custom checkbox-like control, subclass CheckBox or register a dedicated renderer for your custom type rather than reusing CheckBoxRendererBase.

Example fix

// before
[assembly: ExportRenderer(typeof(MyToggle), typeof(CheckBoxRenderer))]

// after
[assembly: ExportRenderer(typeof(CheckBox), typeof(CheckBoxRenderer))]
[assembly: ExportRenderer(typeof(MyToggle), typeof(MyToggleRenderer))]

static bool IsCheckBoxElement(VisualElement element) => element is CheckBox;

When it happens

Trigger: A custom handler/ registrar maps the wrong renderer to CheckBox, or a custom VisualElementRenderer is manually fed a non-CheckBox element. Also occurs when a custom control subclasses a different type but is erroneously registered against CheckBox in the platform registrar.

Common situations: Misconfiguring ExportRenderer attributes (e.g., [assembly: ExportRenderer(typeof(MySwitch), typeof(CheckBoxRenderer))]). Version mismatches where a control assembly exports a renderer for a type that was renamed or moved. Manually invoking SetElement with the wrong element instance in test harnesses.

Related errors

• Element is not of type ImageButton
• element must be of type RadioButton
• {nameof(element)} must be of type {typeof(IndicatorView).Nam
• {nameof(element)} must be of type {typeof(ItemsView).Name}
• {nameof(element)} must be of type {nameof(Button)}

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/38c7eb3004ba599d. Report an issue: GitHub.