Word can't open document after adding CustomXmlPart

Question

I'm trying to add a customxmlPart to a docm file without success. Apparently the file is too big (more than 10mb) to be included in the package.

If the xml file size is less than 7 mb the document can be opened successfully.

Any ideas ?

Thank you for your help.

using (WordprocessingDocument wordDoc = WordprocessingDocument.Open("doc.docm", true))
{
    MainDocumentPart mainPart = wordDoc.MainDocumentPart;

    if (wordDoc.MainDocumentPart.CustomXmlParts != null)
    {
        wordDoc.MainDocumentPart.DeleteParts<CustomXmlPart>(wordDoc.MainDocumentPart.CustomXmlParts);
    }

    CustomXmlPart myXmlPart = mainPart.AddCustomXmlPart(CustomXmlPartType.CustomXml);

    using (FileStream stream = new FileStream("10mbfile.xml", FileMode.Open))
    {
        myXmlPart.FeedData(stream);
    }

    wordDoc.Package.Flush();
}

EDIT : I found the issue, the xml file contains lot of carriage return + line feed. After removing them i can embed the file as a CustomXmlPart.

Answer 1

The following unit test demonstrates that you can add very large custom XML parts (up to 30MB in the example) to a Word document:

using System;
using System.IO;
using System.Linq;
using System.Xml;
using System.Xml.Linq;
using DocumentFormat.OpenXml;
using DocumentFormat.OpenXml.Packaging;
using Xunit;

namespace CodeSnippets.Tests.OpenXml.Wordprocessing
{
    public class LargeCustomXmlPartsTests
    {
        public static readonly XNamespace W = "http://schemas.openxmlformats.org/wordprocessingml/2006/main";

        [Theory]
        [InlineData(5)]
        [InlineData(10)]
        [InlineData(15)]
        [InlineData(20)]
        [InlineData(30)]
        public void CanCreateLargeCustomXmlParts(int size)
        {
            int desiredStreamLength = size * 1024 * 1024;
            string path = $"Document_{size:D2}MB.docm";

            // Create a macro-enabled Word document with a custom XML part having
            // at least the desired size in MB.
            CreateMacroEnabledWordDocument(path, size);

            // Assert that the document does have a custom XML part with at least
            // the desired size.
            using WordprocessingDocument wordDocument = WordprocessingDocument.Open(path, false);
            CustomXmlPart customXmlPart = wordDocument.MainDocumentPart.CustomXmlParts.First();
            using Stream stream = customXmlPart.GetStream(FileMode.Open, FileAccess.Read);
            Assert.True(stream.Length > desiredStreamLength);
        }

        private static void CreateMacroEnabledWordDocument(string path, int size)
        {
            const WordprocessingDocumentType type = WordprocessingDocumentType.MacroEnabledDocument;
            using WordprocessingDocument wordDocument = WordprocessingDocument.Create(path, type);

            // Create a main document part with an empty document.
            MainDocumentPart mainDocumentPart = wordDocument.AddMainDocumentPart();
            WriteRootElement(mainDocumentPart,
                new XElement(W + "document",
                    new XElement(W + "body",
                        new XElement(W + "p"))));

            // Create a custom XML part with the desired size in MB.
            CustomXmlPart customXmlPart = mainDocumentPart.AddCustomXmlPart(CustomXmlPartType.CustomXml);
            WriteRootElement(customXmlPart, CreatePartRootElement(size));
        }

        private static void WriteRootElement(OpenXmlPart part, XElement partRootElement)
        {
            using Stream stream = part.GetStream(FileMode.Create, FileAccess.Write);
            using XmlWriter writer = XmlWriter.Create(stream);

            partRootElement.WriteTo(writer);
        }

        private static XElement CreatePartRootElement(int size)
        {
            var random = new Random();

            return new XElement("root",
                Enumerable.Range(0, size).Select(paragraphIndex =>
                    new XElement("p",
                        new XAttribute("i", paragraphIndex),
                        Enumerable.Range(0, 1000).Select(runIndex =>
                            new XElement("r",
                                new XAttribute("i", runIndex),
                                new XElement("t", CreateRandomString(random)))))));
        }

        private static string CreateRandomString(Random random)
        {
            char[] value = Enumerable
                .Range(0, 930)
                .Select(i => Convert.ToChar(random.Next(33, 125)))
                .ToArray();

            return new string(value);
        }
    }
}

On my Windows 10 notebook, Microsoft Word for Office 365 opens the document with the 30MB custom XML part without any problems. Therefore, I'd say, your problem must be caused by other factors or a combination of factors, including any processing of the custom XML part performed by the VSTO add-in that was mentioned in a comment.

Answer 2

I found the issue, the xml file contains lot of carriage return + line feed. After removing them i can embed the file as a CustomXmlPart.