问使用OpenXML SDK AddAlternativeFormatImportPart后丢失的Word文档方向

EN

for (int i = 0; i < otherDocs.Length; i++)
{
    using (var headerDoc = WordprocessingDocument.Open(headerPath, true))
    {
        var mainPart = headerDoc.MainDocumentPart;

        string altChunkId = "AltChunkId" + i;
        var chunk = mainPart.AddAlternativeFormatImportPart(AlternativeFormatImportPartType.WordprocessingML, altChunkId);

        using (var fileStream = File.Open(otherDocs[i], FileMode.Open))
        {
            chunk.FeedData(fileStream);
        }

        var altChunk = new AltChunk();
        altChunk.Id = altChunkId;
        mainPart.Document.Body.InsertAfter(altChunk, mainPart.Document.Body.Elements<Paragraph>().Last());
        mainPart.Document.Save();

        DocumentWriter.SetPrintOrientation(headerDoc, PageOrientationValues.Landscape);

        headerDoc.Close();
    }
}