void AddAltChunk(MainDocumentPart mainPart, Word.SdtElement sdt, SPFile filename)
{
string altChunkId = "AltChunkId" + id;
id++;
byte[] byteArray = filename.OpenBinary();
AlternativeFormatImportPart chunk = mainPart.AddAlternativeFormatImportPart(
AlternativeFormatImportPartType.WordprocessingML, altChunkId);
using (MemoryStream mem = new MemoryStream())
{
mem.Write(byteArray, 0, (int)byteArray.Length);
mem.Seek(0, SeekOrigin.Begin);
chunk.FeedData(mem);
}
Word.AltChunk altChunk = new Word.AltChunk();
altChunk.Id = altChunkId;
// Replace content control with altChunk information.
OpenXmlElement parent = sdt.Parent;
parent.InsertAfter(altChunk, sdt);
sdt.Remove();
}
