dotnet/wpf · error · ArgumentException

SR.Collection_NoNull

Error message

SR.Collection_NoNull

What it means

The PathFigureCollection(IEnumerable<PathFigure>) constructor throws ArgumentException with SR.Collection_NoNull when the source sequence contains a null PathFigure. Like other Freezable collections, null items are rejected during construction because each item is registered for change notification.

Solutions

  1. Filter nulls before constructing: use collection.Where(f => f != null).
  2. Fix the producer so it never yields null figures.
  3. If nulls are meaningful, model them with an empty PathFigure or a nullable wrapper outside the collection.

Example fix

// before
var figures = new PathFigureCollection(rawFigures);
// after
var figures = new PathFigureCollection(rawFigures.Where(f => f != null));
Defensive patterns

Strategy: validation

Validate before calling

if (collection == null || collection.Any(f => f == null))
    throw new ArgumentException("Source sequence contains null PathFigures");
var figures = new PathFigureCollection(collection);

Type guard

IEnumerable<PathFigure> NonNull(IEnumerable<PathFigure> src) => src?.Where(f => f != null) ?? Enumerable.Empty<PathFigure>();

Try / catch

try
{
    var figures = new PathFigureCollection(source);
}
catch (ArgumentException)
{
    var figures = new PathFigureCollection(source.Where(f => f != null));
}

Prevention

When it happens

Trigger: Constructing a PathFigureCollection from an IEnumerable whose elements include null, e.g. new PathFigureCollection(list) where list contains null entries.

Common situations: Passing LINQ results built from nullable sources; collections populated from parsing where some figures failed to parse and were left null; combining arrays where a placeholder null was left in.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/d2ba15274b3fa4db. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Generated/PathFigureCollection.cs:1022

                _collection = new FrugalStructList<PathFigure>(icollectionOfT);
            }
            else
            {
                ICollection icollection = collection as ICollection;

                if (icollection != null) // an IC but not and IC<T>
                {
                    _collection = new FrugalStructList<PathFigure>(icollection);
                }
                else // not a IC or IC<T> so fall back to the slower Add
                {
                    _collection = new FrugalStructList<PathFigure>();

                    foreach (PathFigure item in collection)
                    {
                        if (item == null)
                        {
                            throw new System.ArgumentException(SR.Collection_NoNull);
                        }
                        PathFigure newValue = item;
                        OnFreezablePropertyChanged(/* oldValue = */ null, newValue);
                        _collection.Add(newValue);

                    }

                    needsItemValidation = false;
                }
            }

            if (needsItemValidation)
            {
                foreach (PathFigure item in collection)
                {
                    if (item == null)
                    {
                        throw new System.ArgumentException(SR.Collection_NoNull);

View on GitHub (pinned to 81131a70a4)