AvaloniaUI/Avalonia · error · FormatException

Invalid PixelSize.

Error message

Invalid PixelSize.

What it means

Thrown by PixelSize.Parse when TryParse fails to interpret the input string. PixelSize expects a 'width,height' or 'widthxheight' formatted string of two non-negative integers. If TryParse returns false (malformed, non-numeric, or negative components), Parse wraps the failure in this FormatException.

Source

Thrown at src/Avalonia.Base/PixelSize.cs:78

        /// <returns>True if the sizes are unequal; otherwise false.</returns>
        public static bool operator !=(PixelSize left, PixelSize right)
        {
            return !(left == right);
        }

        /// <summary>
        /// Parses a <see cref="PixelSize"/> string.
        /// </summary>
        /// <param name="s">The string.</param>
        /// <returns>The <see cref="PixelSize"/>.</returns>
        /// <exception cref="FormatException"/>
        public static PixelSize Parse(string s)
        {
            if (TryParse(s, out var result))
            {
                return result;
            }
            throw new FormatException("Invalid PixelSize.");
        }

        /// <summary>
        /// Try parsing <paramref name="source"/> as <see cref="PixelSize"/>.
        /// </summary>
        /// <param name="source">The <see cref="string"/> to parse.</param>
        /// <param name="result">The result of parsing. if <paramref name="source"/> is not valid <paramref name="result"/> is <see cref="PixelSize.Empty"/> </param>
        /// <returns><c>true</c> if <paramref name="source"/> is valid <see cref="PixelSize"/>, otherwise <c>false</c>.</returns>
        public static bool TryParse([NotNullWhen(true)] string? source,
            out PixelSize result)
        {
            result = Empty;
            if(string.IsNullOrEmpty(source))
            {
                return false;
            }
            using (var tokenizer = new SpanStringTokenizer(source, exceptionMessage: "Invalid PixelSize."))
            {

View on GitHub (pinned to 11c5427268)

Solutions

1. Format the string as two non-negative integers separated by a comma, e.g. '1920,1080'.
2. Prefer PixelSize.TryParse to handle invalid input gracefully without exceptions.
3. Construct PixelSize directly from ints when the values are available programmatically.

Example fix

// before
var size = PixelSize.Parse("1920x1080x extra"); // throws

// after
var size = PixelSize.Parse("1920,1080");
// or safe parse:
if (PixelSize.TryParse(input, out var size)) { /* use size */ }

static PixelSize SafeParsePixelSize(string s)
    => PixelSize.TryParse(s, out var size) ? size : PixelSize.Empty;

try { return PixelSize.Parse(s); }
catch (FormatException) { return PixelSize.Empty; }

When it happens

Trigger: Calling PixelSize.Parse with a string that is not two non-negative integers in the expected delimiter form, e.g. 'abc', '10', '10x-5', or '10;20'. TryParse returns false and Parse throws.

Common situations: Deserializing a size from config/XAML with the wrong delimiter or missing a dimension; user input that omits one component; locale-specific separators (comma vs. period); negative dimensions.

Related errors

• Invalid text trimming string: '{s}'.
• Invalid transform string: '{s}'.
• Too many provided values.
• Invalid value {value.Value} {unitString} for {function}
• Invalid format. {function} expects {count} value(s).

AI-assisted analysis of AvaloniaUI/Avalonia@11c5427268 (2026-08-13). Data as JSON: /api/errors/7a6ddc1282a94822. Report an issue: GitHub.