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Dependency Injection in ASP.NET CoreLinBill2016/8/19

S.O.L.I.DHigh Cohesion & Low Coupling

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3High Cohesion()Low Coupling()

High Cohesion & Low Coupling

4High Coupling

5High CouplingLow Coupling

6Low Cohesion

7Extremely Low Cohesion

8High Cohesion

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Low Coupling & High Cohesion

Inversion of Control &Dependency Injection10

11IoC ()2004 Martin Fowler

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13Dependency Injection()

Program to an interface, not an implementation!abstraction layer: interface, abstract class

14 Context BuilderClassAIServiceAServiceA creates

uses injects dependencies

15public class ObjA{ private IObj obj; public void ObjA(IObj obj) { this.obj = obj; } public void SomeAction() { obj.DoWork(); }}DI Constructor Injection n n

16public class ObjA{ private IObj obj;

public IObj Obj { get { return this.obj; } set { this.obj = value; } } public void SomeAction() { if (this.obj == null) { throw new ArgumentNullException("obj", "obj is null"); } obj.DoWork(); }} public void SomeAction() { obj.DoWork(); }}Property Injection

17public class ObjA{ public void SomeAction(IObj obj) { if (obj == null) { throw new ArgumentNullException("obj", "obj is null"); } obj.DoWork(); }}Method Injection

.NET Core18Mobile First, Cloud FirstOpen SourceCross Platform

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In a press and analyst briefing last year, Microsoft CEO Satya Nadella put up a slide proclaiming Microsoft Linux.

20 Core

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.NET FrameworkAPIsSharedAPIs.NET CoreAPIsWindows APIsWindows UpdatesGUI ArchitectureCross PlatformGitHubNuGetOpen Source

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Getting StartedInstall.NET Core

Create a new .NET Core project:mkdir aspnetcoreappcd aspnetcoreappdotnet new

24{ "version": "1.0.0-*", "buildOptions": { "debugType": "portable", "emitEntryPoint": true }, "dependencies": {}, "frameworks": { "netcoreapp1.0": { "dependencies": { "Microsoft.NETCore.App": { "type": "platform", "version": "1.0.0" }, "Microsoft.AspNetCore.Server.Kestrel": "1.0.0" }, "imports": "dnxcore50" } }}Update theproject.jsonfile to add the Kestrel HTTP server package as a dependency:

25Restore the packages:

Add aStartup.csfile that defines the request handling logic:

dotnet restoreusing System;using Microsoft.AspNetCore.Builder;using Microsoft.AspNetCore.Hosting;using Microsoft.AspNetCore.Http;

namespace aspnetcoreapp{ public class Startup { public void Configure(IApplicationBuilder app) { app.Run(context => { return context.Response.WriteAsync("Hello from ASP.NET Core!"); }); } }}

26Update the code in Program.cs to setup and start the Web host:

Run the app (the command will build the app when its out of date):using System;using Microsoft.AspNetCore.Hosting;

namespace aspnetcoreapp{ public class Program { public static void Main(string[] args) { var host = new WebHostBuilder() .UseKestrel() .UseStartup() .Build();

host.Run(); } }}dotnet rundotnet run

27Browse to http://localhost:5000:

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ASP.NET Core Initialization

Dependency Injection in .NET Core29

30.NET Core DI Container

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ASP.NET Core Web Application

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Web

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project.json

MVC Web API Hosting

35Microsoft project.json .csproj

https://www.infoq.com/news/2016/05/project-json

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Startup.cs

ConfigureServices ASP.NET DI services IServiceCollection ASP.NET 5 DI IServiceCollection Microsoft.Extensions.DependencyInjection

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Configure app IApplicationBuilder UseMvc MVC/Web API ASP.NET

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Run^2 See!

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API Controller

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Web API Controller Constructor ASP.NET controller ITimeService

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Run^2 SeeOops!

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Startup ConfigureServices ITimeService

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Run^2 SeeYeah!

45 IServiceCollection AddScope(why?) ASP.NET DI (LIFO) ITimeService TimeService MVC ValuesController ITimeService DI ITimeService ValuesController

ValueController+ValueController(ItimeService)

ITimeService+Now():string+Now():stringTimeService.NET DI Container()MVC Frameworkcreatesusesinjects dependencies

Bye

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