Adding a .docx Word document to a word processing document using Open XML SDK

Question

I just started using Open XML and am unsure how to insert a file (.docx/.doc) into a word processing document.

I've tried something like the following but get a unknown document error when launching the document with Word 2016.

Using wordprocessingDocument As WordprocessingDocument = WordprocessingDocument.Open(memoryStream, True)
    Using addProcessDoc As WordprocessingDocument = WordprocessingDocument.Open(itemView.Items(i).SubItems(3).Text.ToString, True)
        Dim tempPart = addProcessDoc.MainDocumentPart
        wordprocessingDocument.AddPart(tempPart) 'ERROR: Specified argument was out of the range of valid values.
    End Using
End Using

Answer 1

Inserting an entire document can be achieved using an AltChunk (as described by @VarunRathore here, which allow to embed content such as HTML or OpenXML into another document:

Imports System.Linq
Imports System.IO
Imports DocumentFormat.OpenXml.Packaging
Imports DocumentFormat.OpenXml.Wordprocessing

Class Program

    Private Shared Sub Main(args As String())

        Dim targetFileName As String = "c:\Users\Public\Documents\Target.docx"
        Dim sourceFileName As String = "c:\Users\Public\Documents\Source.docx"
        Dim templateFile As String = "c:\Users\Public\Documents\Template.docx"

        ' create target file from template
        File.Delete(targetFileName)
        File.Copy(templateFile, targetFileName)

        ' open target document
        Using myDoc As WordprocessingDocument = 
            WordprocessingDocument.Open(targetFileName, True)

            Dim altChunkId As String = "AltChunkId1"
            Dim mainPart As MainDocumentPart = myDoc.MainDocumentPart
            Dim chunk As AlternativeFormatImportPart = 
                mainPart.AddAlternativeFormatImportPart(
                    AlternativeFormatImportPartType.WordprocessingML, 
                    altChunkId)

            ' feed the source document into the alt chunk
            Using fileStream As FileStream = File.Open(sourceFileName, FileMode.Open)
                chunk.FeedData(fileStream)
            End Using

            ' insert alt chunk after last paragraph of body
            Dim altChunk As New AltChunk()
            altChunk.Id = altChunkId
            mainPart.Document.Body.InsertAfter(
                altChunk, 
                mainPart.Document.Body.Elements(Of Paragraph)().Last())

            ' save the document
            mainPart.Document.Save()
        End Using

    End Sub

End Class