Now that we know how to use Mapster, we can upgrade our QuizController accordingly. Open the QuizController.cs file and perform the following changes (new/updated lines are highlighted):

using System;
using Microsoft.AspNetCore.Mvc;
using Newtonsoft.Json;
using TestMakerFreeWebApp.ViewModels;
using System.Collections.Generic;
using System.Linq;
using TestMakerFreeWebApp.Data;
using Mapster;

namespace TestMakerFreeWebApp.Controllers
{
    [Route("api/[controller]")]
    public class QuizController : Controller
    {
        #region Private Fields
        private ApplicationDbContext DbContext;
        #endregion

        #region Constructor
        public QuizController(ApplicationDbContext context)
        {
            // Instantiate the ApplicationDbContext through DI
            DbContext = context;
        }
        #endregion Constructor


        #region RESTful conventions methods
        /// <summary>
        /// GET: api/quiz/{id}
        /// Retrieves the Quiz with the given {id}
        /// </summary>
        /// <param name="id">The ID of an existing Quiz</param>
        /// <returns>the Quiz with the given {id}</returns>
        [HttpGet("{id}")]
        public IActionResult Get(int id)
        {
            var quiz = DbContext.Quizzes.Where(i => i.Id == 
              id).FirstOrDefault();
            return new JsonResult(
                quiz.Adapt<QuizViewModel>(),
                new JsonSerializerSettings()
                {
                    Formatting = Formatting.Indented
                });
        }

        /// <summary>
        /// Adds a new Quiz to the Database
        /// </summary>
        /// <param name="m">The QuizViewModel containing the data to 
                            insert</param>
        [HttpPut]
        public IActionResult Put(QuizViewModel m)
        {
            throw new NotImplementedException();
        }

        /// <summary>
        /// Edit the Quiz with the given {id}
        /// </summary>
        /// <param name="m">The QuizViewModel containing the data to 
                                        update</param>
        [HttpPost]
        public IActionResult Post(QuizViewModel m)
        {
            throw new NotImplementedException();
        }

        /// <summary>
        /// Deletes the Quiz with the given {id} from the Database
        /// </summary>
        /// <param name="id">The ID of an existing Test</param>
        [HttpDelete("{id}")]
        public IActionResult Delete(int id)
        {
            throw new NotImplementedException();
        }
        #endregion

        #region Attribute-based routing methods
        /// <summary>
        /// GET: api/quiz/latest
        /// Retrieves the {num} latest Quizzes
        /// </summary>
        /// <param name="num">the number of quizzes to retrieve</param>
        /// <returns>the {num} latest Quizzes</returns>
        [HttpGet("Latest/{num:int?}")]
        public IActionResult Latest(int num = 10)
        {
            var latest = DbContext.Quizzes
                .OrderByDescending(q => q.CreatedDate)
                .Take(num)
                .ToArray();
            return new JsonResult(
                latest.Adapt<QuizViewModel[]>(),
                new JsonSerializerSettings()
                {
                    Formatting = Formatting.Indented
                });
        }

        /// <summary>
        /// GET: api/quiz/ByTitle
        /// Retrieves the {num} Quizzes sorted by Title (A to Z)
        /// </summary>
        /// <param name="num">the number of quizzes to retrieve</param>
        /// <returns>{num} Quizzes sorted by Title</returns>
        [HttpGet("ByTitle/{num:int?}")]
        public IActionResult ByTitle(int num = 10)
        {
            var byTitle = DbContext.Quizzes
                .OrderBy(q => q.Title)
                .Take(num)
                .ToArray();
            return new JsonResult(
                byTitle.Adapt<QuizViewModel[]>(),
                new JsonSerializerSettings()
                {
                    Formatting = Formatting.Indented
                });
        }

        /// <summary>
        /// GET: api/quiz/mostViewed
        /// Retrieves the {num} random Quizzes
        /// </summary>
        /// <param name="num">the number of quizzes to retrieve</param>
        /// <returns>{num} random Quizzes</returns>
        [HttpGet("Random/{num:int?}")]
        public IActionResult Random(int num = 10)
        {
            var random = DbContext.Quizzes
                .OrderBy(q => Guid.NewGuid())
                .Take(num)
                .ToArray();
            return new JsonResult(
                random.Adapt<QuizViewModel[]>(),
                new JsonSerializerSettings()
                {
                    Formatting = Formatting.Indented
                });
        }
        #endregion
    }
}

We did a lot of changes here:

• At the start of the file, we added a reference to the TestMakerFreeWebApp.Data and Mapster required namespaces.
• We added a private DbContext member, which we assign through DI in a new constructor method.
• We used the DbContext to change the behavior of all our data-retrieval methods: Get, Latest, ByTitle, and Random. We got rid of the Dummy Data Provider and used ApplicationDbContext instead, meaning that all the quiz data will now be fetched from our Database from now on.
• We used the .Adapt<TDestination> method of Mapster to map the Quiz entity to the QuizViewModel class anywhere; note how we even mapped Quiz arrays into QuizViewModel arrays, as the library supports them too.