dotnet/wpf · error · ArgumentException

SR.SelectionMustBeServiceProvider

Error message

SR.SelectionMustBeServiceProvider

What it means

TextViewSelectionProcessor.VerifySelection throws ArgumentException(SR.SelectionMustBeServiceProvider) when the selection object passed to a TextView-based selection processor is not an IServiceProvider. TextView selections must expose GetService to yield the underlying ITextView used for anchoring.

Solutions

  1. Pass the ITextView (which is an IServiceProvider) or the document's TextSelection/TextPointer-derived selection the processor expects
  2. Check selection is IServiceProvider and GetService(typeof(ITextView)) returns non-null before calling
  3. Use the matching selection processor for your host (TextSelectionProcessor for text, TreeNodeSelectionProcessor for trees)

Example fix

// before
processor.GetAnchorPoint(someTextRange);
// after
ITextView tv = myTextView; // IServiceProvider
processor.GetAnchorPoint(tv);
Defensive patterns

Strategy: type-guard

Validate before calling

if (selection is IServiceProvider p && p.GetService(typeof(ITextView)) is ITextView)
{ /* safe to call */ }

Type guard

bool IsTextViewSelection(object selection) =>
    selection is IServiceProvider p && p.GetService(typeof(ITextView)) is ITextView;

Try / catch

try { var nodes = processor.GetSelectedNodes(selection); }
catch (ArgumentException ex) when (ex.Message == SR.SelectionMustBeServiceProvider) { /* wrong processor for this selection */ }

Prevention

When it happens

Trigger: Calling GetSelectedNodes/GetParent/GetAnchorPoint on a TextViewSelectionProcessor with a selection object that doesn't implement IServiceProvider (e.g. a raw string, TextRange, or arbitrary object).

Common situations: Mixing selection processors — passing a tree-node UIElement to a text selection processor; custom annotation clients storing non-service-provider selections; refactors changing the selection type.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/b6f70e70ccff799d. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/Annotations/Anchoring/TextViewSelectionProcessor.cs:264

        //
        //  Private Methods
        //
        //------------------------------------------------------        

        #region Private Methods        

        /// <summary>
        ///   Verify the selection is of the correct type.
        /// </summary>
        /// <param name="selection">selection to verify</param>
        /// <returns>the selection cast to the necessary type</returns>
        private ITextView VerifySelection(object selection)
        {
            ArgumentNullException.ThrowIfNull(selection);

            IServiceProvider provider = selection as IServiceProvider;
            if (provider == null)
                throw new ArgumentException(SR.SelectionMustBeServiceProvider, nameof(selection));

            ITextView textView = provider.GetService(typeof(ITextView)) as ITextView;

            return textView;
        }

        #endregion Private Methods

        //------------------------------------------------------
        //
        //  Private Fields
        //
        //------------------------------------------------------

        #region Private Fields

        // ContentLocator part types understood by this processor
        private static readonly XmlQualifiedName[] LocatorPartTypeNames = Array.Empty<XmlQualifiedName>();

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