dotnet/wpf · error · ArgumentException

Property not set.

Error message

Property not set.

What it means

The ExtendedPropertyCollection indexer getter resolves the property by attributeId via GetExtendedPropertyById; when no property with that GUID exists it throws ArgumentException(SR.EPNotFound, nameof(attributeId)) — 'Property not set.' — because reading an unset extended property has no default value.

Solutions

1. Check Contains(attributeId) / HasPropertyData before reading via the indexer.
2. Use TryGetValue-style access by wrapping the read in try/catch for ArgumentException.
3. Ensure the pipeline stage that writes the property always runs before the read.
4. Provide an explicit default value at the call site when the property is optional.

Example fix

// before
var value = properties[attributeId]; // ArgumentException: Property not set.
// after
object value = properties.Contains(attributeId) ? properties[attributeId] : defaultValue;

object value = properties.Contains(attributeId)
    ? properties[attributeId]
    : defaultValue;

static bool TryGetProperty(ExtendedPropertyCollection c, Guid id, out object value)
{
    if (c.Contains(id)) { value = c[id]; return true; }
    value = null; return false;
}

object value;
try { value = properties[attributeId]; }
catch (ArgumentException) { value = defaultValue; /* property not set */ }

When it happens

Trigger: Reading collection[guid] (or GetPropertyData on a Stroke/ContextNode) where the property was never added, or before it was set; checking a property added only conditionally by another code path.

Common situations: Reading optional metadata from ink imported from another application; assuming a property was set by a previous pipeline stage that skipped it; using a GUID from a different ink schema/version.

Understand the failure class

Background: Record Not Found Errors: "not found", RecordNotFound, and "was not found" — what they mean and how to fix them — this error's family across 28 libraries.

Related errors

• The GUID is not part of the ExtendedPropertyCollection.
• ExtendedProperty is already part of the…
• GUID cannot be empty.
• InvalidMatrixContainsInfinity
• InvalidMatrixContainsNaN

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/5b0d3fe5ce3dd0aa. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/MS/internal/Ink/ExtendedPropertyCollection.cs:228

        }

        /// <summary>
        /// Generic accessor for the ExtendedPropertyCollection. 
        /// </summary>
        /// <param name="attributeId">Attribue Id to find</param>
        /// <returns>Value for attribute specified by Id</returns>
        /// <exception cref="System.ArgumentException">Specified identifier was not found</exception>
        /// <remarks>
        /// Note that you can access extended properties via this indexer.
        /// </remarks>
        internal object this[Guid attributeId]
        {
            get
            {
                ExtendedProperty ep = GetExtendedPropertyById(attributeId);
                if (ep == null)
                {
                    throw new ArgumentException(SR.EPNotFound, nameof(attributeId));
                }
                return ep.Value;
            }
            set
            {
                ArgumentNullException.ThrowIfNull(value);
                for (int i = 0; i < _extendedProperties.Count; i++)
                {
                    ExtendedProperty currentProperty = _extendedProperties[i];

                    if (currentProperty.Id == attributeId)
                    {
                        object oldValue = currentProperty.Value;
                        //this will raise events
                        currentProperty.Value = value;

                        //raise change if anyone is listening
                        if (this.Changed != null)

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