AvaloniaUI/Avalonia · warning · ArgumentOutOfRangeException

Give me 5 or more letter please :-)

Error message

Give me 5 or more letter please :-)

What it means

Thrown by ControlCatalog DataValidationViewModel.ExceptionInsideSetterSample setter (ArgumentOutOfRangeException) when the assigned string is null or shorter than 5 characters. Like error 13 this is deliberate sample code showing Avalonia's exception-based data validation surfaced through the binding layer.

Source

Thrown at samples/ControlCatalog/ViewModels/DataValidationViewModel.cs:37

        get => _DataAnnotationsSample;
        set => RaiseAndSetIfChanged(ref _DataAnnotationsSample, value);
    }

    public Func<object, object> Converter { get; } = new Func<object, object>(o =>
    {
        return $"Error: {o}";
    });


    private string? _ExceptionInsideSetterSample;

    public string? ExceptionInsideSetterSample
    {
        get => _ExceptionInsideSetterSample;
        set
        {
            if (value is null || value.Length < 5)
                throw new ArgumentOutOfRangeException(nameof(value), "Give me 5 or more letter please :-)");

            RaiseAndSetIfChanged(ref _ExceptionInsideSetterSample, value);
        }
    }

    public Func<object, object> ExceptionConverter { get; } = new Func<object, object>(o =>
    {
        return o is Exception ex ? $"Huh, there was an Exception: {ex.Message}" : "Something went really wrong!";
    });
}

View on GitHub (pinned to 11c5427268)

Solutions

1. Enter a string of 5 or more characters to pass validation.
2. For real apps, prefer INotifyDataErrorInfo/DataAnnotations over throwing in setters.
3. Wire the binding to tolerate the exception (ValidatesOnExceptions / error template) so the UI shows the message instead of faulting.

Example fix

// before
if (value is null || value.Length < 5)
    throw new ArgumentOutOfRangeException(nameof(value), "Give me 5 or more letter please :-)");

// after
if (value is null || value.Length < 5) { SetError("Min 5 characters"); return; }
RaiseAndSetIfChanged(ref _ExceptionInsideSetterSample, value);

if (value is null || value.Length < 5) { /* flag validation error in UI; do not throw */ return; }

static bool IsValidSample(string? v) => !string.IsNullOrEmpty(v) && v.Length >= 5;

try { vm.ExceptionInsideSetterSample = value; }
catch (ArgumentOutOfRangeException) { /* display as validation error via ExceptionConverter */ }

When it happens

Trigger: Assigning a string that is null or has Length < 5 to ExceptionInsideSetterSample. Bound input (e.g. a TextBox) with fewer than 5 characters triggers it so the UI displays the validation message via ExceptionConverter.

Common situations: Typing 0-4 characters (or clearing) the demo TextBox; demonstrating the 'Huh, there was an Exception' converter path; reproducing validation behavior. Intentional, not a defect.

Related errors

• Value must be less than 10.
• Transition elements have different parents.
• Controls for PageSlide must have same parent.
• Cannot determine visual parent.
• Device with the corresponding LUID not found

AI-assisted analysis of AvaloniaUI/Avalonia@11c5427268 (2026-08-13). Data as JSON: /api/errors/d2bc206756a80e5d. Report an issue: GitHub.