Startup.cs

using System.IO;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using WebApplication.Data;
using WebApplication.Models;
using WebApplication.Services;
using NPoco; 
using Npgsql;

namespace WebApplication
{
    public class Startup
    {
        static private IDatabase _db;

        public Startup(IHostingEnvironment env)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true);

            //if (env.IsDevelopment())
            //{
                // For more details on using the user secret store see https://go.microsoft.com/fwlink/?LinkID=532709
                //builder.AddUserSecrets();
            //}
            builder.AddEnvironmentVariables();

            Configuration = builder.Build();

            _db = new Database(new NpgsqlConnection(Configuration["PostgresConn"]), DatabaseType.PostgreSQL, NpgsqlFactory.Instance); 
        }

        public static IConfigurationRoot Configuration { get; set; }

        public static IDatabase GetDB { get{return _db;}}

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            //https://docs.microsoft.com/en-us/aspnet/core/security/app-secrets
            string pgsqlConnStr = Configuration["PostgresConn"];

            // Add framework services.
            services.AddEntityFrameworkNpgsql()
                .AddDbContext<ApplicationDbContext>(options =>
                options.UseNpgsql(pgsqlConnStr));

            services.AddIdentity<ApplicationUser, IdentityRole>()
                .AddEntityFrameworkStores<ApplicationDbContext>()
                .AddDefaultTokenProviders();

            services.AddMvc();

            // Add application services.
            services.AddTransient<IEmailSender, AuthMessageSender>();
            services.AddTransient<ISmsSender, AuthMessageSender>();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            loggerFactory.AddConsole(Configuration.GetSection("Logging"));
            loggerFactory.AddDebug();
            
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseDatabaseErrorPage();
                app.UseBrowserLink();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
            }

            app.Use(async (context, next) =>
            {
                await next();

                if (context.Response.StatusCode == 404
                    && !Path.HasExtension(context.Request.Path.Value))
                {
                    context.Request.Path = "/index.html";
                    await next();
                }
            });

            app.UseStaticFiles();

            app.UseIdentity();

            //app.UseMvc(); 
            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller=Home}/{action=Index}/{id?}");

                // when the user types in a link handled by client side routing to the address bar 
                // or refreshes the page, that triggers the server routing. The server should pass 
                // that onto the client, so Angular can handle the route
                routes.MapRoute(
                    name: "spa-fallback",
                    template: "{*url}",
                    defaults: new { controller = "Home", action = "Index" }
                );
            });
        }
    }
}