I have an existing XML file that I would like to append without changing the format. Existing File looks like this:
You should use the XmlDocument class to load the whole file, modify it in memory and then write the contents back replacing the original file. Don't worry, it won't mess up your markup, and you can even ask it to preserve non-significant whitespace in the original document using the PreserveWhitespace property (http://msdn.microsoft.com/en-us/library/system.xml.xmldocument.preservewhitespace.aspx).