iOfficeAI/OfficeCLI · critical · InvalidDataException

[Content_Types].xml is empty.

Error message

[Content_Types].xml is empty.

What it means

Thrown when the OPC package manifest [Content_Types].xml exists in the zip but, after the XML prolog is stripped, has zero-length content. [Content_Types].xml is the package's required manifest (not a normal part); an empty one makes the package unusable. The throw is InvalidDataException and is deliberately not caught, unlike other IO failures in that block which return null.

Source

Thrown at src/officecli/Core/RawXmlHelper.cs:1199

        // Special case: `[Content_Types].xml` is the OPC package manifest,
        // not a part. System.IO.Packaging.Package does not expose it; read
        // it as a literal zip entry.
        var trimmed = StripUriSuffixes(partPath.AsSpan().Trim()).ToString();
        if (trimmed.TrimStart('/').Equals("[Content_Types].xml", StringComparison.OrdinalIgnoreCase))
        {
            try
            {
                using var fs = File.Open(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
                using var zip = new ZipArchive(fs, ZipArchiveMode.Read);
                var entry = zip.Entries.FirstOrDefault(e =>
                    e.FullName.Equals("[Content_Types].xml", StringComparison.OrdinalIgnoreCase));
                if (entry == null) return null;
                using var es = entry.Open();
                using var er = new StreamReader(es);
                var ec = er.ReadToEnd();
                var es2 = StripXmlProlog(ec);
                return es2.Length == 0
                    ? throw new InvalidDataException("[Content_Types].xml is empty.")
                    : es2;
            }
            catch (Exception ex) when (ex is not InvalidDataException)
            {
                return null;
            }
        }

        var clean = StripUriSuffixes(partPath.AsSpan().Trim()).ToString();
        var target = clean.StartsWith('/') ? clean : "/" + clean;
        Uri uri;
        try { uri = new Uri(target, UriKind.Relative); } catch { return null; }

        Package bclPkg;
        try
        {
            // FileShare.ReadWrite so we coexist with the SDK's existing handle.
            // Package internally opens the underlying stream with

View on GitHub (pinned to 1ced45e900)

Solutions

  1. Verify the file is a valid OPC package by opening it in Office or unzipping and checking [Content_Types].xml has a <Types> root.
  2. Re-save the document from its originating application to regenerate a valid manifest.
  3. Do not suppress this error — an empty content-types table means no part MIME types resolve, so any further processing is meaningless.
Defensive patterns

Strategy: try-catch

Validate before calling

// Validate the manifest before trusting the package
using var zip = new ZipArchive(File.OpenRead(filePath), ZipArchiveMode.Read);
var ct = zip.Entries.FirstOrDefault(e => e.FullName.Equals("[Content_Types].xml", StringComparison.OrdinalIgnoreCase));
if (ct == null || new StreamReader(ct.Open()).ReadToEnd().Trim().Length == 0)
    throw new InvalidDataException("Package manifest [Content_Types].xml is missing or empty.");

Try / catch

try { var xml = RawXmlHelper.TryReadByZipUri(package, filePath, "[Content_Types].xml"); }
catch (InvalidDataException ex) when (ex.Message.Contains("[Content_Types].xml is empty"))
{ /* abort: package is not a valid OPC container */ }

Prevention

When it happens

Trigger: Calling raw read on '[Content_Types].xml' (or '/[Content_Types].xml') on a package where the entry is present but empty. The content-types branch at RawXmlHelper.cs:1185 reads the literal zip entry.

Common situations: A zip was assembled by hand or by a faulty exporter that created the [Content_Types].xml entry without writing its body. File truncation or a failed save can also leave the manifest empty.

Related errors

AI-assisted analysis of iOfficeAI/OfficeCLI@1ced45e900 (2026-08-13). Data as JSON: /api/errors/5d492aad7e0d00fa. Report an issue: GitHub.