dotnet/wpf · error · ArgumentException

CompoundFile path must be non-empty.

Error message

CompoundFile path must be non-empty.

What it means

CompoundFileStreamReference.SetFullName rejects names that reduce to an empty path: after ConvertBackSlashPathToStringArrayPath yields zero segments, the stream cannot be identified. It throws ArgumentException with SR.CompoundFilePathNullEmpty. A stream name must contain at least one path segment.

Solutions

1. Guard with String.IsNullOrEmpty and require at least one non-segment character before constructing.
2. Validate that the split path yields >= 1 segment before calling the API.
3. Fix upstream code to propagate real names or skip empty entries instead of passing them through.
4. Add input validation at the config/UI boundary.

Example fix

// before
var streamRef = new CompoundFileStreamReference(name); // name may be ""
// after
if (string.IsNullOrWhiteSpace(name) || name.Split('/').All(string.IsNullOrEmpty))
    throw new ArgumentException("Stream name must be a non-empty path.", nameof(name));
var streamRef = new CompoundFileStreamReference(name);

if (string.IsNullOrWhiteSpace(name) || name.Split('/').All(string.IsNullOrEmpty)) throw new ArgumentException("Stream name must be a non-empty path.");

bool IsNonEmptyStreamPath(string name) => !string.IsNullOrEmpty(name) && ContainerUtilities.ConvertBackSlashPathToStringArrayPath(name).Length > 0;

try { new CompoundFileStreamReference(name); }
catch (ArgumentException) { throw new ArgumentException("Non-empty stream path required.", nameof(name)); }

When it happens

Trigger: new CompoundFileStreamReference("") or a name consisting only of separators that produces an empty string array.

Common situations: Uninitialized/default string variables, empty values from config files or user forms, upstream parsing failures yielding empty names.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• SR.CompoundFilePathNullEmpty
• Cannot have leading path delimiter.
• SR.DataSpaceLabelInvalidEmpty
• SR.DelimiterLeading
• Feature ID string cannot have zero length.

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/2d78d02c7acb6a82. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/WindowsBase/MS/Internal/IO/Packaging/CompoundFile/CompoundFileStreamReference.cs:139

        /// </summary>
        /// <remarks>this should only be called from constructors as references are immutable</remarks>
        /// <param name="fullName">string to parse</param>
        /// <exception cref="ArgumentException">if leading or trailing path delimiter</exception>
        private void SetFullName(string fullName)
        {
            ContainerUtilities.CheckStringAgainstNullAndEmpty(fullName, "fullName");

            // fail on leading path separator to match functionality across the board
            // Although we need to do ToUpperInvariant before we do string comparison, in this case
            //  it is not necessary since PathSeparatorAsString is a path symbol
            if (fullName.StartsWith(ContainerUtilities.PathSeparatorAsString, StringComparison.Ordinal))
                throw new ArgumentException(
                    SR.DelimiterLeading, nameof(fullName));

            _fullName = fullName;
            string[] strings = ContainerUtilities.ConvertBackSlashPathToStringArrayPath(fullName);
            if (strings.Length == 0)
                throw new ArgumentException(
                    SR.CompoundFilePathNullEmpty, nameof(fullName));
        }

        //------------------------------------------------------
        //
        //   Private members
        //
        //------------------------------------------------------
        // this can never be null - use String.Empty
        private String _fullName;  // whack-path
    }
}

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