public IQueryable <InstructorViewModel> GetMultiple(Expression <Func <Instructor, bool> > predicate)
        {
            var result = new List <InstructorViewModel>();

            foreach (var instructor in _instructorRepository.GetMultiple(predicate))
            {
                var vm = new InstructorViewModel()
                {
                    Id          = instructor.Id,
                    Name        = instructor.Name,
                    Designation = instructor.Designation,
                    Skill       = instructor.Skill
                };

                result.Add(vm);
            }
            return(result.AsQueryable());
        }