Could not load file or assembly 'System.Windows in WP8.1

Question

An exception of type 'System.IO.FileNotFoundException' occurred in SConnect.exe but was not handled in user code

Additional information: Could not load file or assembly 'System.Windows, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' or one of its dependencies. The system cannot find the file specified.

 Hi iam devoloping a chat app in windows phone 8.1 using xmpp.in my server connection part im getting this strange error.pls help me (in windows phone 8.1)

 

getting in xmpp objclient creation..............=objXmppclient = new XMPPClient();