CoursesController.cs

using Learning.Data;
using Learning.Data.Entities;
using Learning.Web.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using System.Web.Http.Routing;

namespace Learning.Web.Controllers
{
 
    public class CoursesController : BaseApiController
    {
        
        public CoursesController(ILearningRepository repo)
            : base(repo)
        {
        }

        public Object Get(int page = 0, int pageSize = 10)
        {
            IQueryable<Course> query;

            query = TheRepository.GetAllCourses().OrderBy(c => c.CourseSubject.Id);
            var totalCount = query.Count();
            var totalPages = (int)Math.Ceiling((double)totalCount / pageSize);

            var urlHelper = new UrlHelper(Request);
            var prevLink = page > 0 ? urlHelper.Link("Courses", new { page = page - 1, pageSize = pageSize }) : "";
            var nextLink = page < totalPages - 1 ? urlHelper.Link("Courses", new { page = page + 1, pageSize = pageSize }) : "";

            var results = query
                          .Skip(pageSize * page)
                          .Take(pageSize)
                          .ToList()
                          .Select(s => TheModelFactory.Create(s));

            return new
            {
                TotalCount = totalCount,
                TotalPages = totalPages,
                PrevPageLink = prevLink,
                NextPageLink = nextLink,
                Results = results
            };

        }

        public HttpResponseMessage GetCourse(int id)
        {
            try
            {
                var course = TheRepository.GetCourse(id);
                if (course != null)
                {
                    return Request.CreateResponse(HttpStatusCode.OK, TheModelFactory.Create(course));
                }
                else
                {
                    return Request.CreateResponse(HttpStatusCode.NotFound);
                }

            }
            catch (Exception ex)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ex);
            }
        }


        [Learning.Web.Filters.ForceHttps()]
        public HttpResponseMessage Post([FromBody] CourseModel courseModel)
        {
            try
            {

                var entity = TheModelFactory.Parse(courseModel);

                if (entity == null) return Request.CreateErrorResponse(HttpStatusCode.BadRequest, "Could not read subject/tutor from body");

                if (TheRepository.Insert(entity) && TheRepository.SaveAll())
                {
                    return Request.CreateResponse(HttpStatusCode.Created, TheModelFactory.Create(entity));
                }
                else
                {
                    return Request.CreateErrorResponse(HttpStatusCode.BadRequest, "Could not save to the database.");
                }
            }
            catch (Exception ex)
            {
                
                 return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ex);
            }
        }

        [HttpPatch]
        [HttpPut]
        public HttpResponseMessage Put(int id, [FromBody] CourseModel courseModel)
        {
            try
            {

                var updatedCourse = TheModelFactory.Parse(courseModel);

                if (updatedCourse == null) Request.CreateErrorResponse(HttpStatusCode.BadRequest, "Could not read subject/tutor from body");
                
                var originalCourse = TheRepository.GetCourse(id,false);

                if (originalCourse == null || originalCourse.Id != id)
                {
                    return Request.CreateResponse(HttpStatusCode.NotModified, "Course is not found");
                }
                else
                {
                    updatedCourse.Id = id;
                }

                if (TheRepository.Update(originalCourse, updatedCourse) && TheRepository.SaveAll())
                {
                    return Request.CreateResponse(HttpStatusCode.OK, TheModelFactory.Create(updatedCourse));
                }
                else
                {
                    return Request.CreateResponse(HttpStatusCode.NotModified);
                }

            }
            catch (Exception ex)
            {

                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ex);
            }
        }

        public HttpResponseMessage Delete(int id)
        {
            try
            {
                var course = TheRepository.GetCourse(id);
                
                if (course == null)
                {
                    return Request.CreateResponse(HttpStatusCode.NotFound);
                }

                if (course.Enrollments.Count > 0)
                {
                    return Request.CreateResponse(HttpStatusCode.BadRequest, "Can not delete course, students has enrollments in course.");
                }

                if (TheRepository.DeleteCourse(id) && TheRepository.SaveAll())
                {
                    return Request.CreateResponse(HttpStatusCode.OK);
                }
                else
                {
                    return Request.CreateResponse(HttpStatusCode.BadRequest);
                }

            }
            catch (Exception ex)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ex.Message);
            }
        }

    }
}