ASP.NET Core: Reimagining Web Application Development

in .NETIdo Flatow

Senior ArchitectMicrosoft MVP & RD

Sela Group@idoflatow

Agenda• ASP.NET History• ASP.NET Core 1.0 and .NET• ASP.NET Core 1.0 Features• ASP.NET Core MVC

ASP.NET, THEN AND NOW

History of ASP (20 years)• 1996 - Active Server Pages (ASP) • 2002 – ASP.NET• 2005 – ASP.NET 2• 2008 – ASP.NET MVC• 2012 – ASP.NET Web API• 2014 – ASP.NET vNext

– 2015 – ASP.NET 5 RC1– 2016 – ASP.NET Core 1.0 (June 27th, 2016)

Problems with ASP.NET Architecture• Limited hosting possibilities (IIS only)• Dependency on IIS environment (System.Web)• Web evolves faster than the .NET Framework• Requires full-blown .NET Framework • Resource intensive and not web-friendly• Hard to optimize for lightweight high-performance apps• Not completely cloud-optimized

Introducing ASP.NET Core 1.0(Tools in Preview 2)

OS

.NET CLR

ASP.NET MVC(UI + API)

HostSelf-HostedIIS

.NET Core CLRMiddleware

What is Tooling?• Everything that is part of the framework• Command line tools

– dotnet CLI

• Project tools– ASP.NET templates– xproj / csproj

• Visual Studio tools– Configuration IntelliSense– Debugger support

Two Runtimes• .NET Full Framework (4.6)

– Not going away… – Windows hosting with full .NET APIs

• .NET Core 1.0– Subset of the full framework

• No Windows Forms, WPF, Silverlight• No System.Web (WebForms)

– Implemented as set of NuGet packages– Cross-platform and Nano server support

GETTING TO KNOW ASP.NET CORE

ASP.NET Core Features• Flexible and cross-platform runtime• Modular HTTP request pipeline• Unifying MVC, Web API, and Web Pages• Side-by-side versioning with .NET Core• Built-in Dependency Injection• Self-host and IIS-hosted (sort of…)• Open source on GitHub

CREATING A NEW ASP.NET CORE PROJECT

Demo

Solution and Projects• global.json

Project references (in addition to the .sln)• wwwroot

Root for static content (html, css, js, images, etc…)• Program.cs

ASP.NET hosting libraries. This is where it all starts• project.json

References, compiler settings, tooling (replaces web.config and packages.config)

• Startup.csDI and pipeline configuration (replaces global.asax and configuration code)

PROJECT.JSON, STARTUP.CS AND PROGRAM.CS

Demo

ASP.NET Core Middlewares• Improved HTTP performance

– New lean and fast HTTP request pipeline– You choose what to use in your application– By registering middlewares

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerfactory)

{ app.UseExceptionHandler("/Home/Error"); app.UseStaticFiles(); app.UseIdentity(); app.UseMvc(routes => ...)}

Where’s the AppSettings?• Not relying on web.config anymore• New configuration system based on key/value pairs:

– JSON files– INI files– XML files– Environment variables

• Configuration can come from multiple resources– Last resource wins

Loading Settingsvar builder = new ConfigurationBuilder() .SetBasePath(env.ContentRootPath) .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true) .AddXmlFile("appsettings.xml", optional:true) .AddJsonFile($"appsettings.{env.EnvironmentName}.json",true);

if (env.IsDevelopment()){ builder.AddUserSecrets();}

builder.AddEnvironmentVariables();IConfigurationRoot Configuration = builder.Build();...

string connString = Configuration["Data:Default:ConnectionString"];

Dependency Injection• ASP.NET Core is DI-friendly• Basic DI container available throughout the stack• BYOC is also supported (already implemented for Autofac, Dryloc,

StructureMap, etc.)• Out-of-the-box container supports:

– Singleton / Instance – single instance– Transient – new instance each time– Scoped – new instance per request (HTTP context)

• https://github.com/aspnet/DependencyInjection

DI with Controllerspublic class ProductsController : Controller{ private readonly IProductsRepository _repository; public ProductsController(IProductsRepository repository) { this._repository = repository; }

public IActionResult Index() { var products = _repository.GetAllProducts(); return View(products); }}

services.AddTransient<IProductsRepository, DefaultProductsRepository>();

Logging• ASP.NET Core has built-in support for logging• Uses the built-in DI to get a logger instance• Standard logger outputs: category, log level, event Id, and message

• Built-in loggers for:– Console (hosting from cmd/terminal)– TraceSource (good old System.Diagnostics)– Debug (Visual Studio output window)

• Custom loggers are also available (log4net, serilog, elmah, etc.)

• https://github.com/aspnet/Logging

Logging with Controllerspublic class TodoController : Controller{ private readonly ITodoRepository _todoRepository; private readonly ILogger<TodoController> _logger; private const int LIST_ITEMS = 1001;

public TodoController(ITodoRepository todoRepo, ILogger<TodoController> logger) { _todoRepository = todoRepo; _logger = logger; }

[HttpGet] public IEnumerable<TodoItem> GetAll() { _logger.LogInformation(LIST_ITEMS, "Listing all items"); EnsureItems(); return _todoRepository.GetAll(); }}

The dotnet CLI• Cross-platform command line toolchain• Written in .NET Core

• External commands

• https://github.com/dotnet/cli

dotnet newdotnet restoredotnet build --output /stuffdotnet /stuff/new.dlldotnet publish

dotnet efdotnet razor-toolingDotnet aspnet-codegenerator

Hosting ASP.NET Core• ASP.NET Core 1.0 is a stand-alone application

– Uses Kestrel HTTP server (based on libuv, as with node.js)

• Self-hosting with .NET Core– Compiled into a .dll file, hosted by the dotnet CLI

• Self-hosting with .NET 4.6– Compiles into an .exe file– Kestrel or the WebListener server (Windows HTTP.sys)

• IIS-hosted (.NET Core / .NET 4.6)– IIS uses the ASP.NET Core Module to start the self-hosted app– ASP.NET Core template generates the required web.config– Starts either dotnet webapp1.dll or webapp.exe

• https://docs.asp.net/en/latest/hosting/aspnet-core-module.html

CROSS-PLATFORM ASP.NET CORE

Demo

ASP.NET CORE MVC

ASP.NET <= 4.6 FrameworksMVC Web APIWeb Pages

Razor

HTML Helpers HTML Helpers

Controllers Controllers

Actions Actions

Filters Filters

Model binding Model bindingDependency

ResolverDependency

Resolver

ASP.NET Core with MVCMVC Web APIWeb Pages

Razor

HTML Helpers

Controllers

Actions

Filters

Model binding

Dependency Injection

ASP.NET Core MVC • No more duplication - one set of concepts• Used for creating both UI and API• Based on the new ASP.NET Core pipeline• Supports .NET Core• Built DI first• Runs on IIS or self-host• New features in controllers and views

Getting Started with MVC• Project.json

• Startup.cs

"dependencies": { "Microsoft.AspNet.Server.Kestrel": "1.0.0", // Add this: "Microsoft.AspNet.Mvc": "1.0.0"}

// Register MVC default services for DIservices.AddMvc();

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

Web API Configuration• Route configuration -> attribute-based routing • Message handlers -> middleware pipeline• Filters and Formatters -> startup.csservices.AddMvc() .AddXmlDataContractSerializerFormatters() .AddMvcOptions(options => { options.Filters.Add(new ValidatorFilterAttribute()); }) .AddJsonOptions(jsonOptions => { jsonOptions.SerializerSettings.Formatting = Formatting.Indented; });

Controllers – Two in One• UI – same as with MVC 5

• API – similar, but different

public class HomeController : Controller{ public IActionResult Index() { return View(); }}

[Route("api/[controller]")]public class ProductsController : Controller{ [HttpGet("{id:int}")] public Product GetProduct(int id) { return new Product() { ID = id }; }}

Actions – IActionResult[HttpGet("{id:int}", Name = "GetByIdRoute")]public IActionResult GetById (int id){ var item = _items.FirstOrDefault(x => x.Id == id); if (item == null) { return NotFound(); }

return new ObjectResult(item);}

[HttpPost]public IActionResult CreateTodoItem([FromBody] TodoItem item){ _items.Add(item);

return CreatedAtRoute( "GetByIdRoute", new { id = item.Id }, item);}

Showing Some UI for Your API• Swagger - a JSON-based service description framework• Create a Swagger endpoint using Swashbuckle.SwaggerGen

– Browse to /swagger/v1/swagger.json

• Host a built-in UI for testing APIs with Swashbuckle.SwaggerUi– Browse to /swagger/ui

"dependencies": {

"Swashbuckle.SwaggerGen": "6.0.0-beta901",

"Swashbuckle.SwaggerUi": "6.0.0-beta901"

}

services.AddSwaggerGen();

app.UseSwagger();

app.UseSwaggerUi();

Enough with controllers,What about views?

Oh, right!

Injecting Services to Views

• Preferable than using static classes/methods• Use interfaces instead of concrete types• Register in IoC using different lifecycles

public class CatalogService : ICatalogService {

public async Task<int> GetTotalProducts() {...} // From ICatalogService}

@inject MyApp.Services.ICatalogService Catalog<html>

<body><h3>Number of products in the catalog</h3>@await Catalog.GetTotalProducts()

</body></html>

services.AddTransient<ICatalogService, CatalogService>();

Flushing Content with Razor• In ASP.NET <= 5, browser had to wait until

Razor rendered the entire page• Razor now supports flushing, causing HTML to

get chunked (streamed)– @await FlushAsync()

• Not supported when rendering layout sections

Last, but not Least, Tag Helpers• Tag helpers are an alternative to HTML helpers• Tag helpers look like regular HTML elements• Instead of doing this:

• Do this:

• It’s the return of Web Controls, NOOOOOO!!!

@Html.ActionLink("Click me", "AnotherAction")

<a asp-action="AnotherAction">Click me</a>

Tag Helpers are not Evil• Tag Helpers generate markup within their enclosing tag • Less Razor/HTML mess in the .cshtml file• Data-attributes style approach• Use C# to better construct the markup

– Add/remove parts from the inner content– Generate complex HTML (recursive, nested, …)– Cache the output

Existing Tag Helpers• HTML elements

– <a>, <form>, <input>, <label>, <link>, <script>, <select>, <textarea>• Logical

– <cache>• Placeholders

– ValidationSummary (<div>), ValidationMessage (<span>)• You can create your own Tag Helpers

• Check out the source for referencehttps://github.com/aspnet/Mvc/tree/dev/src/Microsoft.AspNetCore.Mvc.TagHelpers

Key Improvements in ASP.NET Core

• Totally modular - Everything is a package• Lightweight - you use minimum set of modules• Faster startup, lower memory footprint• Can be deployed side-by-side with .NET Core• Cross platform - can be hosted anywhere• Better developer experience – DI and one MVC• Everything is open-sourced

Key Improvements in ASP.NET Core

~ 80% less memory

for request footprint

Get Started with ASP.NET Core• Install Visual Studio 2015 / Visual Studio Code• Walkthroughs and samples at http://www.asp.net/core • Documentation at http://docs.asp.net/en/latest • Get the code from http://github.com/aspnet• Read blogs at http://blogs.msdn.com/b/webdev

• @IdoFlatow // idof@sela.co.il // http://www.idoflatow.net/downloads