dotnet/wpf · error · ArgumentException

SR.Collection_NoNull

Error message

SR.Collection_NoNull

What it means

Transform3DCollection.Insert rejects a null Transform3D value and throws ArgumentException with SR.Collection_NoNull. WPF's Freezable-based typed collections disallow null elements because entries feed the render pipeline, which requires a valid transform instance. This mirrors the standard behavior of WPF generated collection types.

Solutions

  1. Check the value for null before calling Insert and skip or substitute a default (e.g. TransformGroup or MatrixTransform.Identity).
  2. Use RemoveAt/Remove instead of inserting null to delete an element.
  3. Fix the upstream source so it produces a real Transform3D instead of null.

Example fix

// before
collection.Insert(0, GetTransform());
// after
var t = GetTransform();
if (t != null) collection.Insert(0, t);
Defensive patterns

Strategy: validation

Validate before calling

if (value == null) throw new ArgumentException(nameof(value));
collection.Insert(index, value);

Type guard

bool IsValid(Transform3D t) => t != null;

Try / catch

try { collection.Insert(i, value); } catch (ArgumentException) { /* substitute default or log */ }

Prevention

When it happens

Trigger: Calling Insert(int index, Transform3D value) with a null value, e.g. collection.Insert(0, null) or inserting the result of a lookup that returned null.

Common situations: Binding a Transform3D from XAML or data where the value failed to resolve; a factory method returning null; refactoring code where a Transform3D field was never initialized.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/c830a6faacde9f76. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media3D/Generated/Transform3DCollection.cs:138

        /// <summary>
        ///     Returns the index of "value" in the list
        /// </summary>
        public int IndexOf(Transform3D value)
        {
            ReadPreamble();

            return _collection.IndexOf(value);
        }

        /// <summary>
        ///     Inserts "value" into the list at the specified position
        /// </summary>
        public void Insert(int index, Transform3D value)
        {
            if (value == null)
            {
                throw new System.ArgumentException(SR.Collection_NoNull);
            }

            WritePreamble();

            OnFreezablePropertyChanged(/* oldValue = */ null, /* newValue = */ value);

            _collection.Insert(index, value);
            OnInsert(value);


            ++_version;
            WritePostscript();
        }

        /// <summary>
        ///     Removes "value" from the list
        /// </summary>
        public bool Remove(Transform3D value)

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