I have an erro while build unity to wp8 . Help me. Please

Unity Engine
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1

Error building Player: Exception: Error: method System.Type System.Type::GetInterface(System.String) doesn’t exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void LitJson.JsonMapper::AddArrayMetadata(System.Type).
Error: method System.Type System.Type::GetInterface(System.String) doesn’t exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void LitJson.JsonMapper::AddObjectMetadata(System.Type).

2

On Windows phone 8.1, some .net api are not supported.

Please refer to

In Unity, you should use api which in WinRTLegacy.dll.
http://docs.unity3d.com/Manual/windowsstore-missingtypes.html