Unity-Technologies/UnityCsReference · error · ArgumentException

The SerializedProperty '{0}' is not supported by BeginProper

Error message

The SerializedProperty '{0}' is not supported by BeginProperty.

What it means

Thrown by GetMaterialSerializedProperty when the SerializedProperty's propertyPath is not one of the four recognized material-level paths (m_LightmapFlags, m_EnableInstancingVariants, m_DoubleSidedGI, m_CustomRenderQueue). BeginProperty only handles these specific material serialization fields; any other property path is rejected.

Source

Thrown at Editor/Mono/Inspector/MaterialEditor.cs:1356

            return count;
        }

        static bool AllTargetsAreVariants(Object[] targets)
        {
            return GetVariantCount(targets) == targets.Length;
        }

        static MaterialSerializedProperty GetMaterialSerializedProperty(SerializedProperty property)
        {
            if (property.propertyPath == "m_LightmapFlags")
                return MaterialSerializedProperty.LightmapFlags;
            if (property.propertyPath == "m_EnableInstancingVariants")
                return MaterialSerializedProperty.EnableInstancingVariants;
            if (property.propertyPath == "m_DoubleSidedGI")
                return MaterialSerializedProperty.DoubleSidedGI;
            if (property.propertyPath == "m_CustomRenderQueue")
                return MaterialSerializedProperty.CustomRenderQueue;
            throw new ArgumentException(string.Format("The SerializedProperty '{0}' is not supported by BeginProperty.", property.propertyPath));
        }

        internal static void BeginProperty(MaterialSerializedProperty property, Object[] targets)
        {
            MaterialProperty.BeginProperty(property, targets);
        }

        internal static void BeginProperty(Rect rect, MaterialSerializedProperty property, Object[] targets)
        {
            MaterialProperty.BeginProperty(rect, null, property, targets);
        }

        public static void BeginProperty(SerializedProperty property)
        {
            MaterialProperty.BeginProperty(GetMaterialSerializedProperty(property), property.serializedObject.targetObjects);
        }

        public static void BeginProperty(Rect rect, SerializedProperty property)

View on GitHub (pinned to 225b0fbdb5)

Solutions

1. Restrict BeginProperty calls to the four known meta property paths; use MaterialProperty.BeginProperty for shader uniforms instead.
2. Guard with a switch/if on property.propertyPath before calling GetMaterialSerializedProperty and skip unknown paths.
3. If you must handle arbitrary paths, catch ArgumentException and fall back to the MaterialProperty-based API.

Example fix

// before
var msp = GetMaterialSerializedProperty(prop); // throws on unknown path
MaterialEditor.BeginProperty(msp, targets);

// after
MaterialProperty matProp = MaterialEditor.GetMaterialProperty(targets, prop.propertyPath);
if (matProp != null)
    MaterialEditor.BeginProperty(matProp, targets);

static readonly HashSet<string> s_KnownPaths = new HashSet<string> {
    "m_LightmapFlags", "m_EnableInstancingVariants", "m_DoubleSidedGI", "m_CustomRenderQueue"
};
bool CanBeginProperty(SerializedProperty p) => s_KnownPaths.Contains(p.propertyPath);

// n/a: discrimination is by string value, not type
static bool IsKnownMaterialPath(SerializedProperty p) =>
    p.propertyPath == "m_LightmapFlags" || p.propertyPath == "m_EnableInstancingVariants"
    || p.propertyPath == "m_DoubleSidedGI" || p.propertyPath == "m_CustomRenderQueue";

try { MaterialEditor.BeginProperty(GetMaterialSerializedProperty(prop), targets); }
catch (ArgumentException) { /* fall back to MaterialProperty.BeginProperty */ }

When it happens

Trigger: Calling BeginProperty indirectly via a custom MaterialEditor/ShaderGUI that iterates over SerializedObject properties and routes an unrecognized path through GetMaterialSerializedProperty. Passing a shader-specific float/vector property (e.g. a user shader uniform) instead of a material-level meta field.

Common situations: Writing a custom ShaderGUI that calls MaterialEditor.BeginProperty for arbitrary shader properties. Version upgrades where property path names changed. Reflecting over the serialized Material object expecting BeginProperty to accept all children.

Related errors

• The MaterialProperty '{0}' should be of type 'Texture' (its
• List of materials contains null
• Could not find MaterialProperty: '{propertyName}', Num prope
• No material targets provided
• Unknown vertex format {format}

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/bd2b2dce7f84684b. Report an issue: GitHub.