AvaloniaUI/Avalonia · error · ArgumentNullException

material

Error message

material

What it means

MaterialExtensions.ToImmutable throws ArgumentNullException(nameof(material)) when the IExperimentalAcrylicMaterial is null. It needs a non-null material to attempt the IMutableExperimentalAcrylicMaterial.ToImmutable() conversion or return the instance unchanged.

Source

Thrown at src/Avalonia.Base/Media/MaterialExtensions.cs:17

using System;

namespace Avalonia.Media
{
    public static class MaterialExtensions
    {
        /// <summary>
        /// Converts a brush to an immutable brush.
        /// </summary>
        /// <param name="material">The brush.</param>
        /// <returns>
        /// The result of calling <see cref="IMutableBrush.ToImmutable"/> if the brush is mutable,
        /// otherwise <paramref name="material"/>.
        /// </returns>
        public static IExperimentalAcrylicMaterial ToImmutable(this IExperimentalAcrylicMaterial material)
        {
            _ = material ?? throw new ArgumentNullException(nameof(material));

            return (material as IMutableExperimentalAcrylicMaterial)?.ToImmutable() ?? material;
        }
    }
}

View on GitHub (pinned to 11c5427268)

Solutions

1. Null-check the material before calling ToImmutable.
2. Initialize the material before use.
3. Provide a default immutable acrylic material as a fallback.

Example fix

// before
var imm = _acrylic.ToImmutable(); // _acrylic may be null

// after
var imm = _acrylic is null ? ExperimentalAcrylicMaterial.Default : _acrylic.ToImmutable();

if (material is null)
    throw new ArgumentNullException(nameof(material));
var imm = material.ToImmutable();

When it happens

Trigger: Calling material.ToImmutable() (the extension method) on a null IExperimentalAcrylicMaterial reference.

Common situations: A null acrylic material field/property being flattened; binding that resolved to null; default-constructed brushes before initialization.

Related errors

• Invalid brush string: '{s}'.
• Unknown CacheMode: {s}
• Invalid color string: '{s}'.
• Invalid color string: '{s.ToString()}'.
• Unable to parse effect: {s}

AI-assisted analysis of AvaloniaUI/Avalonia@11c5427268 (2026-08-13). Data as JSON: /api/errors/8e88c35c31187f2b. Report an issue: GitHub.