Our .NET Web API controllers get their job done; however, they're all affected by a noticeable flaw--the amount of duplicate code we used to make them all behave in the same way, although with different entities. More specifically, this means the following:

• They all have a DbContext property and a constructor that retrieves it through dependency injection
• They all create a number of JsonSerializerSettings objects configured in the same way

This is a rather common issue when working with the MVC pattern, where the same interfaces and approaches are often adopted multiple times and within different controllers.

Luckily enough, repeating a behavior doesn't necessarily mean repeating the code; we can easily cut these dupes with the help of a Base class.

Let's try to put together a Base class for our web API controllers that will take care of the repeating tasks summarized earlier. From Solution Explorer, right-click on the /Controllers/ folder and add a new BaseApiClontroller.cs class file with the following code:

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

namespace TestMakerFreeWebApp.Controllers
{
    [Route("api/[controller]")]
    public class BaseApiController : Controller
    {
        #region Constructor
        public BaseApiController(ApplicationDbContext context)
        {
            // Instantiate the ApplicationDbContext through DI
            DbContext = context;

            // Instantiate a single JsonSerializerSettings object
            // that can be reused multiple times.
            JsonSettings = new JsonSerializerSettings()
            {
                Formatting = Formatting.Indented
            };

        }
        #endregion

        #region Shared Properties
        protected ApplicationDbContext DbContext { get; private set; }
        protected JsonSerializerSettings JsonSettings { get; private 
                                                               set; }
        #endregion
    }
}