XmlDocument not available in Visual Studio 2012 DLL assembly

Question

Using Visual Studio 2012, having created the Portable Class Library project, I would like to use the XmlDocument class . However, the library was not found, even with

using System.Xml;

Error message:

"are you missing a using directive or an assembly reference"

If I right-click links → Add Links, go to the dll directory (address below) and select the following DLL:

C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5\System.XML.dll

Then click OK, an error message appears

"A reference to 'C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5\System.XML.dll' could not be added. 
This component is already automatically referenced by the build system."

Thus, work on using an open source XML parsing library. Any suggestions? Xerces?

But it would be preferable to use the built-in C # XmlDocument class.

Answer 1

, XmlDocument , PCL ( , ). , XDocument - System.Xml.Linq.dll, .

PCL , , .