The errors when I build my project for winphone 8 with electrotank library !

Hi ! I have a project which using electrotank library (create APIs to communicate to server). I have build successfull for android and ios, but for windowphone 8, there are some errors as below:

Error building Player: Exception: Error: method System.String System.Text.Encoding::GetString(System.Byte[]) doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.String Electrotank.Electroserver5.Api.Helper.StreamMessageReader::NextString(). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at Electrotank.Electroserver5.Core.EsEngineDefault. Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at Electrotank.Electroserver5.Core.EsEngineDefault. Error: type System.Timers.Timer doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at Electrotank.Electroserver5.Core.EsEngineDefault. Error: type System.Timers.Timer doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at Electrotank.Electroserver5.Core.EsEngineDefault. Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::.ctor(). Error: method System.Void System.ComponentModel.EventHandlerList::.ctor() doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::.ctor(). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::.ctor(). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::.ctor(). Error: method System.Void System.ComponentModel.EventHandlerList::.ctor() doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::.ctor(). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::.ctor(). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::AddEventHandler(Electrotank.Electroserver5.Api.MessageType,System.Delegate). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::AddEventHandler(Electrotank.Electroserver5.Api.MessageType,System.Delegate). Error: method System.Void System.ComponentModel.EventHandlerList::AddHandler(System.Object,System.Delegate) doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::AddEventHandler(Electrotank.Electroserver5.Api.MessageType,System.Delegate). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::AddEventListener(Electrotank.Electroserver5.Api.MessageType,Electrotank.Electroserver5.Core.EsEngine/EsDelegate`1). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::AddEventListener(Electrotank.Electroserver5.Api.MessageType,Electrotank.Electroserver5.Core.EsEngine/EsDelegate`1). Error: method System.Void System.ComponentModel.EventHandlerList::AddHandler(System.Object,System.Delegate) doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::AddEventListener(Electrotank.Electroserver5.Api.MessageType,Electrotank.Electroserver5.Core.EsEngine/EsDelegate`1). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::Raise(Electrotank.Electroserver5.Api.EsMessage). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::Raise(Electrotank.Electroserver5.Api.EsMessage). Error: method System.Delegate System.ComponentModel.EventHandlerList::get_Item(System.Object) doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::Raise(Electrotank.Electroserver5.Api.EsMessage). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::Raise(Electrotank.Electroserver5.Api.EsMessage). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::Raise(Electrotank.Electroserver5.Api.EsMessage). Error: method System.Delegate System.ComponentModel.EventHandlerList::get_Item(System.Object) doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::Raise(Electrotank.Electroserver5.Api.EsMessage). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::RemoveEventHandler(Electrotank.Electroserver5.Api.MessageType,System.Delegate). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::RemoveEventHandler(Electrotank.Electroserver5.Api.MessageType,System.Delegate). Error: method System.Void System.ComponentModel.EventHandlerList::RemoveHandler(System.Object,System.Delegate) doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::RemoveEventHandler(Electrotank.Electroserver5.Api.MessageType,System.Delegate). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::RemoveEventListener(Electrotank.Electroserver5.Api.MessageType,Electrotank.Electroserver5.Core.EsEngine/EsDelegate`1). Error: type System.ComponentModel.EventHandlerList doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::RemoveEventListener(Electrotank.Electroserver5.Api.MessageType,Electrotank.Electroserver5.Core.EsEngine/EsDelegate`1). Error: method System.Void System.ComponentModel.EventHandlerList::RemoveHandler(System.Object,System.Delegate) doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core.EsEngineDefault::RemoveEventListener(Electrotank.Electroserver5.Api.MessageType,Electrotank.Electroserver5.Core.EsEngine/EsDelegate`1). Error: type System.Timers.Timer doesn't exist in target framework. It is referenced from Assembly-CSharp.dll at System.Void Electrotank.Electroserver5.Core..

Can anybody help/explain me? Thanks,