StreamWriter myFile = new StreamWriter(path);
myFile.Write(xml);
myFile.Close();

  <character>
    <CharacterString>utf8</CharacterString>
  </character>

<?xml version="1.0" encoding="utf-8"?>
<MD_Metadata xmlns="http://www.isotc211.org/2005/gmd">
  <language>
    <CharacterString>de</CharacterString>
  </language>
  <characterSet>
    <CharacterString>keiner</CharacterString>
  </characterSet>
  <hierarchyLevel>
    <CharacterString>eins</CharacterString>
  </hierarchyLevel>
  <hierarchyLevelName>
    <CharacterString>dataset</CharacterString>
  </hierarchyLevelName>
</MD_Metadata>