Original: ASP.NET Core project configuration (Startup) - ASP.NET Core Basics Tutorial - simple tutorial, simple programming

ASP.NET Core project configuration (Startup)

The previous chapters we have introduced and used Startup categories, including

Modified when creating a new project Startup class Hello World modify the return value
In the previous chapter to explain Program.cs talked about when Program the class is instantiated Startup class

But Startup can do more than that, it can be said ASP.NET Core in large and small are various components and middleware and Startup class deal.

But all can not finish a chapter. Ever since, this chapter we will explain a few things most important

previous version

If you've ever used ASP.NET, then you might expect

See a global.asax file, a place you can write code to perform during start-up Web applications
See a web.config file that contains all the configuration parameters for the application to be executed

In ASP.NET Core, these files all but disappeared, replaced by the use of Startup.cs load configuration and startup code

Startup.cs file has a Startup class, in this class you can configure the application, even Configuring source

The default file content Startup.cs

Startup.cs file in the default content below

the using the System ;
 the using the System.Collections.Generic ; the using the System.Linq ; the using System.Threading.Tasks ; the using Microsoft.AspNetCore.Builder ; the using Microsoft.AspNetCore.Hosting ; the using Microsoft.AspNetCore.Http ; the using Microsoft.Extensions.DependencyInjection ; namespace the HelloWorld { public class the Startup { // this method is called at run time. // You can use this method to add the service to the container // For more information about configuring the application, you can view https://go.microsoft.com/fwlink/?LinkID=398940public void ConfigureServices ( IServiceCollection Services ) { } // This method is invoked at run time // This method can be used to configure the HTTP request pipeline public void the Configure ( IApplicationBuilder App , IHostingEnvironment the env ) { IF ( the env . IsDevelopment ()) { App . UseDeveloperExceptionPage (); } App . the Run ( the async ( context ) => { the awaitcontext.Response.WriteAsync("Hello World!"); }); } } }

Startup Class

Startup Class can be used to define the configuration request processing pipeline and application services required.

Startup Class must be public, and must include the following two methods

ConfigureServices() 方法
```
public void ConfigureServices(IServiceCollection services){}
```
ConfigureServices() The method used to define the services needed by the application, such as ASP.NET Core MVC, Entity Framework Core Identity and etc.

About the service we will further detail in the following sections
Configure () method
```
public void Configure(IApplicationBuilder app, IHostingEnvironment env){}
```
Configure() It is used to define the request pipeline middleware

On request pipeline concept, we will detail in the next section

Project Configuration

Startup Class Configure() where a method for configuring and constructing the HTTP request pipeline

How to understand the Bible?

In fact, that is to say, Configure() the method can be used to define our application how to respond to the request

For any web site, by default it will only output Hello World！

If we want different behavior of the application, we need Configure() to add additional code to change the method in pipeline

For example, if we want to, such as index.html serving static files and the like, you need to Configure() add some code method

For example, if you want to send an error page or routing requests to the ASP.NET MVC controller, we need this Configure() to do some work methods

Dynamic response content

By default, we have provided in response to a hard-coded for each request Hello World!

Took over to us no longer use hard-coded, but load a string from a component to respond to each request

In Solution Manager HelloWorld right-click on the item and select Add -> New File

If your computer is Windows, it is the Add -> New Item
In the New File dialog box, select the left of the Web , and then select the right of the empty JSON file

If your computer is Windows, it is first checked ASP.NET Core under conventional (Genreral) and then select JSON file
Enter the name AppSettings.json , then click the lower-right corner of the New button to add a AppSettings.json file

If your computer is Windows, then clicking on Add button

Then double-click AppSettings.json open the file, enter the following

{
    "Message": "Hello World \ n Hello, simple tutorial, your website is www.twle.cn it!?"
}

Double-click to open the Startup.cs file, Startup add a read-write property class Configuration
```
public IConfiguration Configuration { get; set; }
```

Modified Startup class, adding Startup() a constructor, loading AppSettings.json file and then builds CI

public Startup() 
{ 
    var builder = new ConfigurationBuilder().AddJsonFile("AppSettings.json"); 
    Configuration = builder.Build(); 
}

Last modified Configure() method, read from the configuration item message and a content of the response

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }

    app.Run(async (context) =>
    {
        var msg = Configuration["message"];
        await context.Response.WriteAsync(msg);
    });
}

The modified code is completed as follows

Startup.cs

using System;
using System.IO; using System.Collections.Generic; using System.Linq; using System.Threading.Tasks; using Microsoft.AspNetCore.Builder; using Microsoft.AspNetCore.Hosting; using Microsoft.AspNetCore.Http; using Microsoft.Extensions.DependencyInjection; using Microsoft.Extensions.Configuration; namespace HelloWorld { public class Startup { public Startup() { var builder = new ConfigurationBuilder() .SetBasePath(Directory.GetCurrentDirectory()) .AddJsonFile("AppSettings.json"); Configuration = builder.Build(); } public IConfiguration Configuration { get; set; } // This method gets called by the runtime. Use this method to add services to the container. // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940 public void ConfigureServices(IServiceCollection services) { } // This method gets called by the runtime. Use this method to configure the HTTP request pipeline. public void Configure(IApplicationBuilder app, IHostingEnvironment env) { if (env.IsDevelopment()) { app.UseDeveloperExceptionPage(); } app.Run(async (context) => { var msg = Configuration["message"]; await context.Response.WriteAsync(msg); }); } } }

Click the green triangle Run the project (if the project has been directly refresh the browser can be run)

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