How to fix "Root element is missing." when doing a Visual Studio (VS) Build?

In my case it was the xxxxxxxxxxxx.vcxproj.user file that was causing the problem; it was blank after a crash. I renamed it and the problem went away.

Make sure any XML file (or any file that would be interpreted as an XML file by visual studio) has a correct XML structure - that is, one root element (with any name, I have use rootElement in my example):

<?xml version="1.0"?> 
<rootElement>
 ...
</rootElement>

You will also get 'root element is missing' when the BOM strikes :). BOM = byte order mark. This is an extra character that gets added to the start of a file when it is saved with the wrong encoding.
This can happen sometimes in Visual Studio when working with XML files. You can either code something to remove it from all your files, or if you know which file it is you can force visual studio to save it with a specific encoding (utf-8 or ascii IIRC).

If you open the file in an editor other than VS (try notepad++), you will see two funny characters before the <? xml declaration.

To fix this in VS, open the file in VS and then depending on the version of VS

• File > Advanced Save Options > choose an appropriate encoding
• File > Save As > keep the filename, click the drop-down arrow on the right side of the save button to select an encoding

In my case.I was getting missing element error pointing to NuGet.Config file. At that time it was looking some thing like this

<?xml version="1.0" encoding="utf-8"?>
<settings>
  <repositoryPath>Packages</repositoryPath>
</settings>

then I just added configuration tag that actually wraps entire xml. Now working fine for me

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <settings>
     <repositoryPath>Packages</repositoryPath>
  </settings>
</configuration>