private async void BtnSave_Click(object sender, EventArgs e)
        {
            var _driving_test_application = await _driving_test_applicationsService.GetById <Model.DrivingTestApplications>(_id);

            DrivingTestApplicationsInsertRequest insertRequest = new DrivingTestApplicationsInsertRequest
            {
                InstructorId = _driving_test_application.InstructorId,
                CategoryId   = _driving_test_application.CategoryId,
                CandidateId  = _driving_test_application.CandidateId,
                Date         = _driving_test_application.Date.Date,
                Active       = checkBoxActive.Checked == true ? true : false,
                Passed       = checkBoxPolozenPrakticniTest.Checked,
            };
            await _driving_test_applicationsService.Update <Model.DrivingTestApplications>(_id, insertRequest);

            var instructorId = _driving_test_application.InstructorId;
            var categoryId   = _driving_test_application.CategoryId;
            var candidateId  = _driving_test_application.CandidateId;
            var instructor_Category_Candidate = await _instructor_categories_candidatesService.GetById <Model.Instructor_Category_Candidate>(instructorId, categoryId, candidateId);

            InstructorCategoryCandidateInsertRequest instructorCategoryCandidateInsertRequest = new InstructorCategoryCandidateInsertRequest
            {
                PolozenTeorijskiTest  = instructor_Category_Candidate.PolozenTeorijskiTest,
                PolozenTestPrvePomoci = instructor_Category_Candidate.PolozenTestPrvePomoci,
                PolozenPrakticniTest  = checkBoxPolozenPrakticniTest.Checked,
                Prijavljen            = checkBoxActive.Checked == true ? true : false,
                NumberOfLessons       = instructor_Category_Candidate.NumberOfLessons,
                Paid = instructor_Category_Candidate.Paid,
                Date = (instructor_Category_Candidate.Date != null) ? (DateTime?)instructor_Category_Candidate.Date.Value : null,
            };
            await _instructor_categories_candidatesService.Update <Model.Instructor_Category_Candidate>(instructorId, categoryId, candidateId, instructorCategoryCandidateInsertRequest);
        }
        public async Task Submit(object candidates)
        {
            var Candidates = candidates as List <Candidate>;
            DrivingTestApplicationsInsertRequest insert_request = new DrivingTestApplicationsInsertRequest();



            var instructors_categories = await _instructor_categoriesService.GetAll <List <Instructor_Category> >(request2);

            InstructorCategoryCandidateSearchRequest request3 = new InstructorCategoryCandidateSearchRequest();
            InstructorCategoryCandidateInsertRequest request4 = new InstructorCategoryCandidateInsertRequest();
            int count = 0;

            foreach (var instructor_category in instructors_categories)
            {
                request3.InstructorId = instructor_category.InstructorId;
                request3.CategoryId   = instructor_category.CategoryId;
                foreach (var candidate in Candidates)
                {
                    request3.CandidateId           = candidate.Id;
                    request3.PolozenTeorijskiTest  = true;
                    request3.PolozenTestPrvePomoci = true;
                    request3.PolozenPrakticniTest  = false;
                    request3.Prijavljen            = false;
                    var instructors_categories_candidates = await _instructor_categories_candidateService.GetAll <List <Instructor_Category_Candidate> >(request3);

                    foreach (var instructor_category_candidate in instructors_categories_candidates)
                    {
                        insert_request.InstructorId = instructor_category_candidate.InstructorId;
                        insert_request.CategoryId   = instructor_category_candidate.CategoryId;
                        insert_request.CandidateId  = instructor_category_candidate.CandidateId;
                        insert_request.Date         = DateTime.Now.Date;
                        insert_request.Passed       = false;
                        insert_request.Active       = true;
                        await _driving_test_applicationsService.Insert <DrivingTestApplications>(insert_request);

                        count++;
                        request4.PolozenTestPrvePomoci = instructor_category_candidate.PolozenTestPrvePomoci;
                        request4.PolozenTeorijskiTest  = instructor_category_candidate.PolozenTeorijskiTest;
                        request4.PolozenPrakticniTest  = instructor_category_candidate.PolozenPrakticniTest;
                        request4.Prijavljen            = true;
                        request4.NumberOfLessons       = instructor_category_candidate.NumberOfLessons;
                        request4.Paid = instructor_category_candidate.Paid;
                        await _instructor_categories_candidateService.Update <Instructor_Category_Candidate>(instructor_category_candidate.InstructorId, instructor_category_candidate.CategoryId, instructor_category_candidate.CandidateId, request4);
                    }
                }
            }
            await Application.Current.MainPage.DisplayAlert("", "You have successfully submitted " + count + " request", "OK");
        }