Only one top level element is allowed in an XML document

Answer 1

Open it in Notepad and see what the output is, and from there see what the error really is, and post it here if you need more help.

Answer 2

Well, this is quite normal. An XML document must have a root element that is not duplicated. You have already asked the related question here and originally here. Jon Skeet quite succinctly explained this to you already.

If there is an issue in understanding, you should consider reading up on XML or doing some research, instead of asking the same question repeatedly because most people will not realize that you have already received excellent answers to the problem.

If you keep doing the same thing you've already done, you should not expect different results.