dotnet/maui · error · ArgumentException

element must be of type RadioButton

Error message

element must be of type RadioButton

What it means

Thrown by RadioButtonRenderer.SetElement when the VisualElement passed to the renderer is not a RadioButton. The AppCompat RadioButton renderer is bound exclusively to the RadioButton control type; receiving any other element indicates a misregistered handler or incorrect element assignment.

Source

Thrown at src/Compatibility/Core/src/Android/AppCompat/RadioButtonRenderer.cs:78

			((IElementController)Element).SetValueFromRenderer(VisualElement.IsFocusedPropertyKey, hasFocus);
		}

		SizeRequest IVisualElementRenderer.GetDesiredSize(int widthConstraint, int heightConstraint)
		{
			Measure(widthConstraint, heightConstraint);
			return new SizeRequest(new Size(MeasuredWidth, MeasuredHeight));
		}

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

			if (!(element is RadioButton))
			{
				throw new ArgumentException($"{nameof(element)} must be of type {nameof(RadioButton)}");
			}

			RadioButton oldElement = Element;
			Element = (RadioButton)element;

			Performance.Start(out string reference);

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

			element.PropertyChanged += OnElementPropertyChanged;

			if (_tracker == null)
			{
				// Can't set up the tracker in the constructor because it access the Element (for now)
				SetTracker(new VisualElementTracker(this));

View on GitHub (pinned to f377ff1c5e)

Solutions

1. Verify the ExportRenderer/handler registration maps RadioButton (and only RadioButton) to RadioButtonRenderer.
2. Confirm the element passed is a RadioButton, not a CheckBox, Switch, or custom control.
3. For custom radio-button-like controls, subclass RadioButton or register a dedicated renderer for your type.

Example fix

// before
[assembly: ExportRenderer(typeof(CheckBox), typeof(RadioButtonRenderer))]

// after
[assembly: ExportRenderer(typeof(RadioButton), typeof(RadioButtonRenderer))]

static bool IsRadioButtonElement(VisualElement element) => element is RadioButton;

When it happens

Trigger: An ExportRenderer attribute maps a non-RadioButton type to RadioButtonRenderer, or the renderer is manually invoked with the wrong element. Also surfaces when a custom control masquerading as a radio button is registered against the wrong renderer.

Common situations: Confusing RadioButton with CheckBox or a custom toggle control in ExportRenderer attributes. Version upgrades where RadioButton's namespace changed. Reusing RadioButtonRenderer for a custom selection control without subclassing RadioButton.

Related errors

• Element is not of type CheckBox
• Element is not of type ImageButton
• {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/94f070a6ce2434af. Report an issue: GitHub.