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ExcelReaderFactory.CreateReader throwing exception for End of Central Directory mismatch when called with a MemoryStream

See original GitHub issue

Given the following:

private static void diffZipArchiveEntry(ZipArchiveEntry zipArchiveEntry1, ZipArchiveEntry zipArchiveEntry2)
    using (var stream1 = zipArchiveEntry1.Open())
    using (var stream2 = zipArchiveEntry2.Open())
    using (var xlsxReader1 = ExcelReaderFactory.CreateReader(stream1))
    using (var xlsxReader2 = ExcelReaderFactory.CreateReader(stream2))
        // compare the two streams

A System.NotSupportedException is thrown on the factory method. Just wanted to see if this intentional or not and whether I have to hit the disk and extract these .zip files before comparing the .xlsx inside them or whether it’s another issue entirely.

Issue Analytics

  • State:closed
  • Created 5 years ago
  • Comments:5

github_iconTop GitHub Comments

andersnmcommented, Mar 26, 2018


ExcelDataReader requires a seekable stream as input, and after verifying with a little program, it appears ZipArchiveEntry.Open() does not return a seekable stream.

To avoid the disk, there’s also an option to extract into a MemoryStream and pass that to the ExcelReaderFactory, if appropriate for your use case.

            var zip = System.IO.Compression.ZipFile.OpenRead("..\\..\\");
            var entry = zip.Entries[0];
            var stream = entry.Open();
            Console.WriteLine("Can seek: " + stream.CanSeek.ToString());

            // Output:
            // Can seek: False
ateccecommented, Mar 27, 2018

Rofl. Looks like I tried to load the same stream into a memory stream twice. Thanks for all your help!

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