Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Versioning;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using my_book.Data;
using my_book.Data.Models;
using my_book.Data.Services;
using my_book.Exceptions;

namespace my_book
{
    public class Startup
    {
        public string ConnectionString { get; set; }
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
            ConnectionString = Configuration.GetConnectionString("DefaultConnectionString");
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();

            //Configure DBContext with SQL
            services.AddDbContext<AppDbContext>(options => options.UseSqlServer(ConnectionString));

            //Configure the Services
            services.AddTransient<BookService>();
            services.AddTransient<PublishersService>();
            services.AddTransient<AuthorsService>();
            services.AddApiVersioning(config => {
                config.DefaultApiVersion = new ApiVersion(1,0);
                config.AssumeDefaultVersionWhenUnspecified = true;

                config.ApiVersionReader = new HeaderApiVersionReader("custom-version-header");
               // config.ApiVersionReader = new MediaTypeApiVersionReader();

            });
            services.AddSwaggerGen(c =>
           {
               c.SwaggerDoc("v1", new Microsoft.OpenApi.Models.OpenApiInfo { Title = "mybook", Version = "v1" });
           });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseSwagger();
                app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "my-books v1"));
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            //Exception Handling
            app.ConfigureBuilderExceptionHandler();
            //app.ConfigureCustomExceptionHandler();
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });

            //AppDbInitializer.Seed(app);
        }
    }
}