Editing docx with openxml returns invalid memorystream

Question

I created a DLL that takes a Word template, I have code that edits the document using openXML then the result is sent via memory stream to a web service where the documents is downloaded to the user. The issue is that the memory stream is sending is either the original template document without the updates OR sends the updated Word document XML format where the document is obviously corrupted. Here is the code:

string strTemplate = AppDomain.CurrentDomain.BaseDirectory + "Report Template.docx";

WordprocessingDocument wdDocument;

//stream the template
byte[] fileBytes = File.ReadAllBytes(strTemplate);
MemoryStream memstreamDocument = new MemoryStream();

memstreamDocument.Write(fileBytes, 0, (int)fileBytes.Length);

wdDocument = WordprocessingDocument.Open(memstreamDocument, true);

//CODE TO UPDATE TEMPLATE

//Save entire document
wdDocument.MainDocumentPart.Document.Save();

After saving the document, if using the following code the memory stream returns the original template without any updates to the document:

return memstreamDocument;

If using the following code the memory stream returns the openXML data with the updates but the document is corrupted:

MemoryStream memstreamUpdatedDocument = new MemoryStream();
Stream streamDocument = wdDocument.MainDocumentPart.GetStream();
streamDocument.CopyTo(memstreamUpdatedDocument);
return memstreamUpdatedDocument;

Here is my code in the web service which works fine:

HttpResponse response = HttpContext.Current.Response;
MemoryStream stream = GR.GetReport("", intReportID, Culture, ConnectionString, false);

response.Clear();
response.ClearHeaders();
response.ClearContent();
response.AddHeader("content-disposition", "attachment; filename=\"" + "Report_" + intReportID+ ".docx\"");
response.ContentType = "application/vnd.openxmlformats-officedocument.wordprocessingml.document";
response.ContentEncoding = Encoding.GetEncoding("ISO-8859-1");
stream.Position = 0;
stream.CopyTo(response.OutputStream);
response.End();
return response;

Answer 1

After reviewing the supplied code I have provided a modified code snippet that should fit your needs of returning a modified MemoryStream from a file template using the WordprocessingDocument class by OpenXML. Your web service code snippet provided should work as is.

// file path of template
string strTemplate = AppDomain.CurrentDomain.BaseDirectory + "Report Template.docx";

// create FileStream to read from template
FileStream fsTemplate = new FileStream(strTemplate, FileMode.Open, FileAccess.Read);

// create MemoryStream to copy template into and modify as needed
MemoryStream msDocument = new MemoryStream();

// copy template FileStream into document MemoryStream
fsTemplate.CopyTo(msDocument);

// close the template FileStream as it is no longer necessary
fsTemplate.Close();

// reset cursor position of document MemoryStream back to top 
// before modifying
msDocument.Position = 0;

// create WordProcessingDocument using the document MemoryStream
using (WordprocessingDocument wdDocument = WordprocessingDocument.Open(msDocument, true)) {

    //Access the main Workbook part, which contains all references.
    MainDocumentPart mainPart = wdDocument.MainDocumentPart;

    /* ... CODE TO UPDATE TEMPLATE ... */

    // save modification to main document part
    wdDocument.MainDocumentPart.Document.Save();

   // close wdDocument as it is no longer needed
   wdDocument.Close();
}

// reset cursor position of document MemoryStream back to top
msDocument.Position = 0;

// return memory stream as promised
return msDocument;