unoplatform/uno · error · ArgumentException

This converter does not use any parameters. You should remov

Error message

This converter does not use any parameters. You should remove "{parameter}" passed as parameter.

What it means

Thrown by FromNullableBoolToCustomValueConverter.Convert when a ConverterParameter was supplied in the XAML binding. The converter ignores parameters by design, so any non-null parameter is treated as a programmer error rather than silently dropped.

Source

Thrown at src/SamplesApp/SamplesApp.Samples/Windows_UI_Xaml_Controls/CommandBar/CommandBar_Native_With_AppBarButton_Binding.xaml.cs:46

	public sealed partial class CommandBar_Native_With_AppBarButton_Binding : Page
	{
		public CommandBar_Native_With_AppBarButton_Binding()
		{
			this.InitializeComponent();
		}
	}

	public class FromNullableBoolToCustomValueConverter : IValueConverter
	{
		public object NullOrFalseValue { get; set; }

		public object TrueValue { get; set; }

		public object Convert(object value, Type targetType, object parameter, string language)
		{
			if (parameter != null)
			{
				throw new ArgumentException($"This converter does not use any parameters. You should remove \"{parameter}\" passed as parameter.");
			}

			if (value != null && !(value is bool))
			{
				throw new ArgumentException($"Value must either be null or of type bool. Got {value} ({value.GetType().FullName})");
			}

			if (value == null || !System.Convert.ToBoolean(value, CultureInfo.InvariantCulture))
			{
				return NullOrFalseValue;
			}
			else
			{
				return TrueValue;
			}
		}

		public object ConvertBack(object value, Type targetType, object parameter, string language)

View on GitHub (pinned to 0418340488)

Solutions

Remove the ConverterParameter=... from the XAML binding that uses this converter.
If you need parameterized behavior, use a different converter that supports it, or add a property to the converter and set it as a resource.
Search the XAML for the converter's StaticResource key and audit every usage.

Example fix

<!-- before -->
<Binding Path="IsOn" Converter="{StaticResource FromNullableBoolToCustomValue}" ConverterParameter="Foo" />
<!-- after -->
<Binding Path="IsOn" Converter="{StaticResource FromNullableBoolToCustomValue}" />

Defensive patterns

Strategy: validation

Validate before calling

<!-- In XAML, ensure the binding has no ConverterParameter -->
<!-- Use a static check: grep the page for 'ConverterParameter' on this converter's bindings -->

Prevention

Document converters that take no parameter and audit XAML for stray ConverterParameter.
Use distinct resource keys so the right converter is obvious in bindings.
Add an XML doc comment on the converter class stating 'no ConverterParameter'.

When it happens

Trigger: XAML binding like {Binding IsOn, Converter={StaticResource C}, ConverterParameter=Foo} passes 'Foo' as parameter, which the Convert method rejects at the top.

Common situations: Copy-pasting a binding from a converter that does take a parameter (e.g. a visibility converter) into one that doesn't; leftover ConverterParameter from refactoring; misunderstanding which converter is being used.

Related errors

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/498fe7805eacd5a1. Report an issue: GitHub.