Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.IO;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Antiforgery;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.EntityFrameworkCore;
using Angular_ASPNETCore_CustomersService.Repository;
using Microsoft.Extensions.Hosting;
using Microsoft.OpenApi.Models;

namespace Angular_ASPNETCore_CustomersService
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        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)
        {
            //Add PostgreSQL support
            //services.AddDbContext<CustomersDbContext>(options => {
            //    options.UseNpgsql(Configuration.GetConnectionString("CustomersPostgresConnectionString"));
            //});

            //Add SQL Server support
            //services.AddDbContext<CustomersDbContext>(options => {
            //    options.UseSqlServer(Configuration.GetConnectionString("CustomersSqlServerConnectionString"));
            //});

            //Add SqLite support
            services.AddDbContext<CustomersDbContext>(options => {
                options.UseSqlite(Configuration.GetConnectionString("CustomersSqliteConnectionString"));
            });

            services.AddControllersWithViews();

            // Handle XSRF Name for Header
            services.AddAntiforgery(options => {
                options.HeaderName = "X-XSRF-TOKEN";
            });

            //https://github.com/domaindrivendev/Swashbuckle.AspNetCore
            services.AddSwaggerGen(options =>
            {
                options.SwaggerDoc("v1", new OpenApiInfo
                {
                    Version = "v1",
                    Title = "Application API",
                    Description = "Application Documentation",
                    Contact = new OpenApiContact { Name = "Author" },
                    License = new OpenApiLicense { Name = "MIT", Url = new Uri("https://en.wikipedia.org/wiki/MIT_License") }
                });
            });

            services.AddCors(o => o.AddPolicy("AllowAllPolicy", options =>
            {
                options.AllowAnyOrigin()
                        .AllowAnyMethod()
                        .AllowAnyHeader()
                        .WithExposedHeaders("X-InlineCount");
            }));

            services.AddCors(o => o.AddPolicy("AllowSpecific", options => 
                    options.WithOrigins("http://localhost:4200")
                           .WithMethods("GET", "POST", "PUT", "PATCH", "DELETE")
                           .WithHeaders("accept", "content-type", "origin", "X-InlineCount")
                           .WithExposedHeaders("X-InlineCount")));

            services.AddScoped<ICustomersRepository, CustomersRepository>();
            services.AddScoped<IStatesRepository, StatesRepository>();
            services.AddTransient<CustomersDbSeeder>();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, 
            IWebHostEnvironment env, 
            CustomersDbSeeder customersDbSeeder, 
            IAntiforgery antiforgery)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
            }

            // This would need to be locked down as needed (very open right now)
            app.UseCors("AllowAllPolicy");
            
            app.UseStaticFiles();

            // Enable middleware to serve generated Swagger as a JSON endpoint
            app.UseSwagger();

            // Enable middleware to serve swagger-ui assets (HTML, JS, CSS etc.)
            // Visit http://localhost:5000/swagger
            app.UseSwaggerUI(c =>
            {
                c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
            });

            // Manually handle setting XSRF cookie. Needed because HttpOnly 
            // has to be set to false so that Angular is able to read/access the cookie.
            app.Use((context, next) =>
            {
                string path = context.Request.Path.Value;
                if (path != null && !path.ToLower().Contains("/api"))
                {
                    var tokens = antiforgery.GetAndStoreTokens(context);
                    context.Response.Cookies.Append("XSRF-TOKEN", 
                        tokens.RequestToken, new CookieOptions { HttpOnly = false }
                    );
                }

                return next();
            });

            // For 3.0
            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();

                endpoints.MapControllerRoute(
                     name: "default",
                     pattern: "{controller}/{action}/{id?}");

                // Handle redirecting client-side routes to Customers/Index route
                endpoints.MapFallbackToController("Index", "Home");
            });

            customersDbSeeder.SeedAsync(app.ApplicationServices).Wait();
        }
    }
}