List item Title goes blank after editing document in Word

Question

I am creating new document in document library using this code:

private SPListItem CreateNewDocument()
{
    SPContentType documentContentType;   
    byte[] bytes;
    string templatePath;
    SPFile template;
    SPFolder folder;
    string documentFileName;
    string documentPath;
    SPFile document;

    documentContentType = this.workflowProperties.Web.ContentTypes[this.contentType];

    bytes = new byte[0];
    if (!string.IsNullOrEmpty(documentContentType.DocumentTemplateUrl))
    {
        templatePath = documentContentType.DocumentTemplateUrl;
        template = this.workflowProperties.Web.GetFile(templatePath);
        bytes = template.OpenBinary();
    }

    folder = this.workflowProperties.Web.Folders[this.documentLibraryListTitle];
    documentFileName = string.Format(Constants.msWordDocumentFileNameFormat, this.documentTitle);
    documentPath = Path.Combine(folder.Url, documentFileName);
    document = this.workflowProperties.Web.Files.Add(documentPath, bytes, true);

    return document.Item;
}

Then in the next method, I am assigning property values to the document:

private void SetDocumentProperties(SPListItem item)
{
    SPUser author;

    author = workflowProperties.Web.AllUsers[this.documentAutor];

    item[SPBuiltInFieldId.Title] = this.documentTitle;
    item[SPBuiltInFieldId.ContentTypeId] = this.workflowProperties.Web.ContentTypes[this.contentType].Id;
    item[Constants.documentAuthorField] = author;
    item.UpdateOverwriteVersion();
}

All this works well and the document gets created with all properties filled properly. However, when I open the file manually, edit it in MS Word and then save it back to the document library, the Title field is blank. I would appreciate if someone could explain why is this happening and how to fix it? Thanks.

Answer 1

Solved this one. It appears that the DOCX documents cannot be of size zero and that they need at least a MainPart in order not to be corrupt. Having the proper DOCX file solves the issue with the missing title property.