demo.cs

public void ConfigureServices(IServiceCollection services)
        {
            services.AddDbContext<AppDbContext>(options => options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

            services
                .AddMvc()
                .AddJsonOptions(
                    options => options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
                )
                .SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

            // In production, the Angular files will be served from this directory
            services.AddSpaStaticFiles(configuration =>
            {
                configuration.RootPath = "ClientApp/dist";
            });

            services.AddScoped<Repository>();
            services.AddScoped<Seeder>();

            services.AddScoped<IDependencyResolver>(x => new FuncDependencyResolver(x.GetRequiredService));

            services.AddScoped<DataSchema>();

            services.AddGraphQL(x =>
            {
                x.ExposeExceptions = true; //set true only in development mode. make it switchable.
            })
            .AddGraphTypes(ServiceLifetime.Scoped);
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env, Seeder seeder)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseStaticFiles();
            app.UseSpaStaticFiles();

            app.UseGraphQL<DataSchema>();
            app.UseGraphQLPlayground(new GraphQLPlaygroundOptions());

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

            var post = File.ReadAllText(@"wwwroot/post.json");
            var comment = File.ReadAllText(@"wwwroot/comment.json");
            seeder.Seedit(post, comment);

            app.UseSpa(spa =>
            {
                // To learn more about options for serving an Angular SPA from ASP.NET Core,
                // see https://go.microsoft.com/fwlink/?linkid=864501

                spa.Options.SourcePath = "ClientApp";

                if (env.IsDevelopment())
                {
                    spa.UseAngularCliServer(npmScript: "start");
                }
            });
        }