How to force XDocument to output the prolog in uppercase while preserving identation and formatting?

Question

I want XDocument to output the XML prolog (for example \"\") in uppercase.

Here is how I\'m cur

Answer 1

XDocument xdoc = new XDocument();

.... // do your stuff here

string finalDoc = xdoc.ToString();
string header = finalDoc.Substring(0,finalDoc.IndexOf("?>") + 2); // end of header tag

finalDoc = finalDoc.Replace(header, header.ToUpper());  // replace header with the uppercase version

.... // do stuff with the xml with the upper case header

EDIT:

Oh you only want the UTF-8 upper case?

Then this is more correct:

XDocument xdoc = new XDocument();

.... // do your stuff here

string finalDoc = xdoc.ToString();
string header = finalDoc.Substring(0,finalDoc.IndexOf("?>") + 2); // end of header tag
string encoding = header.Substring(header.IndexOf("encoding=") + 10);
encoding = encoding.Substring(0,encoding.IndexOf("\""); // only get encoding content

// replace encoding with the uppercase version in header, then replace old header with new one.
finalDoc = finalDoc.Replace(header, header.Replace(encoding, encoding.ToUpper()));

.... // do stuff with the xml with the upper case header

This will only replace whatever is in the encoding to uppercase manually.