Why does XDecleration ignores the encoding parameter i set

The problem

I am trying to generate a XML file with the XDeclaration that should spit out the following

<?xml version="1.0"?>.

What I keep getting when I run my piece of code is this

<?xml version="1.0" encoding="utf-8"?>.

So the problem is, no matter what I change in the encoding parameter of my XDecleration it keeps adding a encoding tag to my declaration.

My question

Is what I want even possible? And if so could someone explain it to me?

What I have tried

First I tried to set OmitXmlDeclaration to true. But that removes my declaration entirely and then I can't use the XDecleration class at all..

Secondly, when I set my XDecleration to this:

new XDeclaration("1.0", string.Empty, "yes")

I get this

<?xml version="1.0" encoding="utf-8" standalone="yes"?>

and when I set my XDecleration to this:

new XDeclaration("1.0", string.Empty, string.Empty)

I get this

<?xml version="1.0" encoding="utf-8"?>

So I know that it does respond to what I enter, but the encoding part is not.

My Code

   public FileResult Download() 
      {
            var doc = new XDocument(
                        new XDeclaration("1.0", string.Empty, string.Empty),
                        new XElement("foo", 
                            new XAttribute("hello", "world")
                        )
                    );

            using (var stream = new MemoryStream())
            {
                var settings = new XmlWriterSettings()
                {
                    OmitXmlDeclaration = false,
                    Indent = true,
                };

                using (var writer = XmlWriter.Create(stream, settings))
                {
                    doc.Save(writer);                    
                }

                stream.Position = 0;

                return File(stream.ToArray(), "text/xml", "HelloWorld.xml");
            }      
      }