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System.UnauthorizedAccessException - MemoryStream's internal buffer cannot be accessed

 When trying to read a MemoryStream I got the following error message:

Here is the code I was using:

var template=File.ReadAllBytes("template.docx");
var templateStream=new MemoryStream(template);
//WmlDocument is part of OpenXML PowerTools
var wmlDoc = new WmlDocument(new OpenXmlPowerToolsDocument(filename, templateStream));
view raw MemoryStream.cs hosted with ❤ by GitHub

Couldn't be any simpler but unfortunately it didn't work. 

I couldn't figure out what I did wrong...until I noticed the following in the documentation:

This constructor does not expose the underlying stream. GetBuffer throws UnauthorizedAccessException.

Aha, it seems that the OpenXmlPowerToolsDocument is calling GetBuffer behind the scenes. So we need to use a different constructor:

 

var template=File.ReadAllBytes("template.docx")
var templateStream = new MemoryStream(template,0, template.Length,writable:false, publiclyVisible:true);
//WmlDocument is part of OpenXML PowerTools
var wmlDoc = new WmlDocument(new OpenXmlPowerToolsDocument(filename, templateStream));
view raw MemoryStreamFixed.cs hosted with ❤ by GitHub

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