意外的实体对象错误

我有以下代码:

public IList<T_CLIENT> Get_All_Obj()
{
    try
    {
        IList<T_CLIENT> LesListe;
        using (FaExpedEntities oEntite_T = new FaExpedEntities())
        {
            var query = from o in oEntite_T.T_CLIENT select o;
            LesListe = query.ToList();
        }
        return LesListe;
    }
    catch (Exception excThrown)
    {
        throw new Exception("Err_02", excThrown);
    }
}

但是我不知道为什么我得到这些错误:

Error 1 The type 'System.Data.Objects.DataClasses.EntityObject'is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Data.Entity, Version = 4.0.0.0, Culture = neutral, PublicKeyToken = b77a5c561934e089'. C: ' Soft8 ' FA_Exped ' Code ' FrontEnd ' FaExped_FrontEnd_WebApp_Domaine ' FaExped_FrontEnd_WebApp_Business ' Le_T ' LeTclientusrstatus_Entite_BL.cs 15 42 FaExped_FrontEnd_WebApp_Business
Error 2 c: ' Soft8 ' FA_Exped ' Code ' FrontEnd ' FaExped_FrontEnd_WebSite ' Login.aspx.cs (8): error CS0246: The type or namespace name 'FaExped_FrontEnd_WebApp_Business' not found (a using directive or a reference to 'assembly is it missing?)
Error 3 'FaExped_FrontEnd_WebApp_Domaine.FaExpedEntities': type used in a using statement must be implicitly convertible to 'System.IDisposable'C: ' Soft8 ' FA_Exped ' Code ' FrontEnd ' FaExped_FrontEnd_WebApp_Domaine ' FaExped_FrontEnd_WebApp_Business ' Le_T ' LeTclient_Entite_BL.cs 22 17 FaExped_FrontEnd_WebApp_Business

如何修复这些错误?

var entities = new FaExpedEntities();
return entities.T_CLIENT.ToList();