public Task <IContactGroup> GetContactGroupAsync(int number)
 {
     return(ExecuteAsync(async() =>
     {
         using ContactGroupModelHandler contactGroupModelHandler = new ContactGroupModelHandler(DbContext, ContactModelConverter.Create());
         return await contactGroupModelHandler.ReadAsync(number);
     },
                         MethodBase.GetCurrentMethod()));
 }
        public Task <IContactGroup> CreateContactGroupAsync(IContactGroup contactGroup)
        {
            NullGuard.NotNull(contactGroup, nameof(contactGroup));

            return(ExecuteAsync(async() =>
            {
                using ContactGroupModelHandler contactGroupModelHandler = new ContactGroupModelHandler(DbContext, ContactModelConverter.Create());
                return await contactGroupModelHandler.CreateAsync(contactGroup);
            },
                                MethodBase.GetCurrentMethod()));
        }