public async Task <IDataResult <ICollection <Student> > > GetStudentsWithAddressAsync() { var students = await _studentDal.GetStudentsWithAddress(); if (students == null) { return(new ErrorDataResult <ICollection <Student> >(new List <Student>(), HttpStatusCode.NotFound)); } return(new SuccessfulDataResult <ICollection <Student> >(students, HttpStatusCode.OK)); }