dotnet/wpf · error · ArgumentNullException

annotation component

Error message

annotation component

What it means

The AdornerPresentationContext constructor throws ArgumentNullException with name "annotation component" when a non-null AnnotationAdorner is supplied but its AnnotationComponent property is null. An adorner presented in an annotation context must carry its AnnotationComponent; a subsequent InvalidOperationException guards components already in another presentation context.

Solutions

  1. Set the adorner's AnnotationComponent before constructing the AdornerPresentationContext
  2. Construct the AnnotationComponent and pass it to the AnnotationAdorner constructor
  3. If the component is intentionally absent, pass null for the adorner parameter instead

Example fix

// before
var adorner = new AnnotationAdorner(); // AnnotationComponent never set
new AdornerPresentationContext(layer, adorner);
// after
var adorner = new AnnotationAdorner(myAnnotationComponent);
new AdornerPresentationContext(layer, adorner);
Defensive patterns

Strategy: validation

Validate before calling

if (adorner != null && adorner.AnnotationComponent == null)
    throw new InvalidOperationException("Adorner must have an AnnotationComponent before creating AdornerPresentationContext.");

Type guard

bool HasAnnotationComponent(AnnotationAdorner adorner) => adorner?.AnnotationComponent != null;

Try / catch

try { var ctx = new AdornerPresentationContext(layer, adorner); }
catch (ArgumentNullException) { /* initialize AnnotationComponent and retry */ }
catch (InvalidOperationException) { /* component already presented elsewhere — detach first */ }

Prevention

When it happens

Trigger: Constructing AdornerPresentationContext(adornerLayer, adorner) where adorner.AnnotationComponent was never set or was cleared; creating a bare AnnotationAdorner without associating a component.

Common situations: Custom adorner subclasses forgetting to initialize AnnotationComponent; component lifetime teardown clearing the reference before context creation; wiring adorners manually instead of through AnnotationService.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/41cdbf5d117236e9. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/Annotations/Component/AdornerPresentationContext.cs:44

    internal sealed class AdornerPresentationContext : PresentationContext
    {
        #region Constructors

        /// <summary>
        /// Create an initialized instance of an AdornerPresentationContext. Set the presentation context of the 
        /// component wrapped in the adorner
        /// </summary>
        /// <param name="adornerLayer">AdornerLayer this presentation context is on, must not be null</param>
        /// <param name="adorner">AnnotationAdorner that wraps the annotation component.  Will be null in case of creating enclosing context</param>
        private AdornerPresentationContext(AdornerLayer adornerLayer, AnnotationAdorner adorner)
        {
            ArgumentNullException.ThrowIfNull(adornerLayer);

            _adornerLayer = adornerLayer;
            if (adorner != null)
            {
                if (adorner.AnnotationComponent == null)
                    throw new ArgumentNullException("annotation component");
                if (adorner.AnnotationComponent.PresentationContext != null)
                    throw new InvalidOperationException(SR.Format(SR.ComponentAlreadyInPresentationContext, adorner.AnnotationComponent));
                _annotationAdorner = adorner;
            }
        }

        #endregion Constructors

        #region Static Methods

        /// <summary>
        /// Host a component in an adorner layer.
        /// Wrap the component in an annotation adorner, add that to the adorner layer, create and set presentation context and invalidate to pick up styles.
        /// Note, this is called from two places: (1) component manager to host choosen annotation component, and (2) presentation context when component
        /// adds additional IAnnotationComponent.
        /// </summary>
        /// <param name="adornerLayer">Adorner layer the component is hosted in</param>
        /// <param name="component">Component that is being hosted</param>

View on GitHub (pinned to 81131a70a4)