dotnet/maui · error · XamlParseException

Expected {nameof(Setter)} but found {parents[4]}.

Error message

Expected {nameof(Setter)} but found {parents[4]}.

What it means

XamlParseException raised in FindTypeForVisualState when, in the Style-attached visual-state path, parents[4] is not a Setter. After confirming VisualStateGroupList at parents[3], the converter expects the value context to ultimately be rooted in a Setter; finding something else means the Setter.Property resolution cannot infer the target type from the chain.

Source

Thrown at src/Controls/src/Core/BindablePropertyConverter.cs:149

			// Skip 0; we would not be making this check if TargetObject were not a Setter
			// Skip 1; we would not be making this check if the immediate parent were not a VisualState

			// VisualStates must be in a VisualStateGroup
			if (parents[2] is not VisualStateGroup)
				throw new XamlParseException($"Expected {nameof(VisualStateGroup)} but found {parents[2]}.", lineInfo);

			// Are these Visual States directly on a VisualElement?
			if (parents[3] is VisualElement vsTarget)
				return vsTarget.GetType();

			if (parents[3] is not VisualStateGroupList)
				throw new XamlParseException($"Expected {nameof(VisualStateGroupList)} but found {parents[3]}.", lineInfo);

			if (parents[4] is VisualElement veTarget)
				return veTarget.GetType();

			if (parents[4] is not Setter)
				throw new XamlParseException($"Expected {nameof(Setter)} but found {parents[4]}.", lineInfo);

			if (parents[5] is TriggerBase trigger)
				return trigger.TargetType;

			// These must be part of a Style; verify that 
			if (parents[5] is Style style)
				return style.TargetType;

			throw new XamlParseException($"Unable to find a TragetType for the Bindable Property. Try prefixing it with the TargetType.", lineInfo);

		}

		public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
		{
			if (value is not BindableProperty bp)
				throw new NotSupportedException();
			return $"{bp.DeclaringType.Name}.{bp.PropertyName}";
		}

View on GitHub (pinned to f377ff1c5e)

Solutions

  1. Ensure each Setter sits directly in the Setters collection and the Property attribute is on the Setter.
  2. Re-create the VisualState/Setter markup from a known-good template.
  3. Validate the Style/Setters/VisualStateManager nesting against the docs.

Example fix

<!-- before: Setter placed where converter expects a different node -->
<VisualStateGroupList>
  <VisualStateGroup>
    <VisualState>
      <VisualState.Setters>
        <!-- mis-nested nodes -->
      </VisualState.Setters>
    </VisualState>
  </VisualStateGroup>
</VisualStateGroupList>

<!-- after -->
<VisualStateGroupList>
  <VisualStateGroup>
    <VisualState x:Name="N">
      <VisualState.Setters>
        <Setter Property="VisualElement.BackgroundColor" Value="Red" />
      </VisualState.Setters>
    </VisualState>
  </VisualStateGroup>
</VisualStateGroupList>
Defensive patterns

Strategy: validation

Validate before calling

// Keep Setter as the direct parent of the resolved Property attribute within
// VisualState.Setters.

Try / catch

try { /* compile */ }
catch (XamlParseException ex) when (ex.Message.Contains("Setter"))
{
    // verify Setter placement in the visual-state chain
}

Prevention

When it happens

Trigger: A VisualState nested in a Style's VisualStateGroupList where the immediate parent of the property reference is not a Setter; malformed Setters collection that places a Setter in the wrong slot; a Setter whose Property is being resolved outside its expected position.

Common situations: Editing Style/Setters XAML by hand and displacing a Setter; tool output that interleaves Setters with other nodes incorrectly.

Related errors

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/32c48abfb75a6668. Report an issue: GitHub.