dotnet/wpf · error · ArgumentException

PROPSPEC union selector is unrecognized.

Error message

PROPSPEC union selector is unrecognized.

What it means

ManagedFilter's ManagedPropSpec validates the PropSpecType union selector: only Id and Name are supported. Setting any other PROPSPEC selector (e.g., pointer-based lpwstr variants or other union members) throws ArgumentException because the managed wrapper cannot represent it.

Solutions

1. Use only PropSpecType.Id (property ID) or PropSpecType.Name (string name) selectors.
2. Convert unsupported selectors before passing: resolve numeric IDs or names on the caller side.
3. Catch ArgumentException from the PropType setter and map/normalize the spec type first.

Example fix

// before
spec.PropType = PropSpecType.Pointer; // throws
// after
spec.PropType = PropSpecType.Id;
spec.PropId = 2; // or use PropSpecType.Name with a string name

if (propSpec.Type != PropSpecType.Id && propSpec.Type != PropSpecType.Name) throw new ArgumentException("Only Id or Name PROPSPEC selectors are supported", nameof(propSpec));

static bool IsSupportedPropSpec(PropSpec s) => s.Type == PropSpecType.Id || s.Type == PropSpecType.Name;

try { wrapper.PropType = spec.Type; } catch (ArgumentException) { /* normalize to Id/Name or skip */ }

When it happens

Trigger: Constructing a ManagedPropSpec or setting its PropType to a PropSpecType value other than PropSpecType.Id or PropSpecType.Name.

Common situations: Marshaling native PROPSPEC structs from IFilter/property-system code that uses numeric/pointer selectors; copy-pasting property-spec code using FullPropSpec types not covered by the wrapper.

Related errors

• SR.NeedToBeComVisible
• 0x80004002
• 0x80040200
• 0x80040202
• 0x80041702

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/7662d422bbd5334d. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/IO/Packaging/ManagedFilter.cs:47

        /// <value></value>
        internal PropSpecType PropType
        {
            get
            {
                return _propType;
            }
// The following code is not being compiled, but should not be removed; since some container-filter
// plug-in (e.g. metadata) may use it in future.
#if false
            set
            {
                switch (value)
                {
                    case PropSpecType.Id: break;
                    case PropSpecType.Name: break;

                    default:
                        throw new ArgumentException(SR.FilterPropSpecUnknownUnionSelector, "propSpec");
                }
                _propType = value;
            }
#endif
        }

        /// <summary>
        /// Property name (only valid if PropType is Name
        /// </summary>
        /// <value></value>
        internal string PropName
        {
            get
            {
                System.Diagnostics.Debug.Assert(_propType == PropSpecType.Name, "ManagedPropSpec.PropName - PropName only meaningful if PropType is type string");
                return _name;
            }
            set

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