dotnet/wpf · error · ArgumentException

SR.CanNotCompareDiffTypes

Error message

SR.CanNotCompareDiffTypes

What it means

CompoundFileStorageReference.CompareTo(object) requires its argument to be another CompoundFileStorageReference. When passed a non-null object of a different type it throws ArgumentException with SR.CanNotCompareDiffTypes. Comparisons are done ordinal-insensitively on the upper-invariant full name, which only makes sense between same-type references.

Solutions

1. Ensure every element compared is a CompoundFileStorageReference; filter or partition mixed collections before sorting.
2. Use type-safe generic collections (List<CompoundFileStorageReference>) so the compiler enforces element type.
3. Compare against null first if you want the standard 'any reference sorts after null' behavior (CompareTo already returns 1 for null).
4. If comparing across reference kinds, compare on a shared key (e.g. FullName string) instead of CompareTo.

Example fix

// before
list.Contains(mixedObject); // mixed List<object> sorted -> ArgumentException
// after
var storages = list.OfType<CompoundFileStorageReference>().ToList();
storages.Sort(); // only same-type references compared

if (other is CompoundFileStorageReference) { /* safe to sort */ }

bool IsComparableStorageRef(object o) => o is CompoundFileStorageReference;

try { result = storageRef.CompareTo(obj); }
catch (ArgumentException) { result = string.CompareOrdinal(storageRef.FullName, obj?.ToString()); }

When it happens

Trigger: Calling CompareTo on a CompoundFileStorageReference and passing an object of any other type (e.g. a CompoundFileStreamReference, string, or unrelated class); also occurs indirectly via Sort()/ArrayList.Sort on mixed-type collections.

Common situations: Sorting mixed lists of storage and stream references in custom packaging tools, comparing references from different compound-file implementations, or passing parsed strings instead of reference objects.

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

• Cannot compare different types.
• ' ' ID is not a valid XSD ID.
• Cannot create a read-only stream.
• Cannot have leading path delimiter.
• CompoundFile path must be non-empty.

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/3be9a1fa40637bd7. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/WindowsBase/MS/Internal/IO/Packaging/CompoundFile/CompoundFileStorageReference.cs:85

        #endregion

        #region IComparable
        /// <summary>
        /// Compares two CompoundFileReferences
        /// </summary>
        /// <param name="o">CompoundFileReference to compare to this one</param>
        /// <remarks>Supports the IComparable interface</remarks>
        /// <returns>less than zero if this instance is less than the given reference, zero if they are equal
        /// and greater than zero if this instance is greater than the given reference</returns>
        int IComparable.CompareTo(object o)
        {
            if (o == null)
                return 1;   // Standard behavior.

            // different type?
            if (o.GetType() != GetType())
                throw new ArgumentException(
                    SR.CanNotCompareDiffTypes);

            // Note that because of the GetType() checking above, the casting must be valid.
            CompoundFileStorageReference r = (CompoundFileStorageReference)o;
            return String.CompareOrdinal(_fullName.ToUpperInvariant(), r._fullName.ToUpperInvariant());
        }
        #endregion

        //------------------------------------------------------
        //
        //   Private Methods
        //
        //------------------------------------------------------
        /// <summary>
        /// Assign the fullName
        /// </summary>
        /// <param name="fullName">name</param>
        /// <remarks>cache a duplicate copy of the storage name to save having to do this for 

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