认证

using System;
using System.Collections.Generic;
using System.Security.Claims;
using System.Security.Principal;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace ConsoleApp2
{
    class Program
    {
        private static readonly Dictionary<string, string> Accounts = new Dictionary<string, string>
        {
            {"Admin", "123"}, {"UserA", "123"}, {"UserB", "123"}
        };

        public static void Main(string[] args)
        {
            Host.CreateDefaultBuilder()
                .ConfigureWebHostDefaults(builder => builder
                    .ConfigureServices(collection => collection
                        .AddRouting()
                        .AddAuthentication(options =>                                                //注册认证中间件，cook验证权限
                            options.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme)
                        .AddCookie())
                    .Configure(app => app
                        .UseAuthentication()                                                       //使用权限
                        .UseRouting()                                                              //使用路由
                        .UseEndpoints(endpoints =>                                                 
                        {
                            endpoints.Map("/", RenderHomePageAsync);                                //委托和路由映射关系，没有登陆到首页
                            endpoints.Map("Account/Login", SignInAsync);                           //委托和路由映射关系，登陆，默认路径
                            endpoints.Map("Account/Logout", SignOutAsync);                          //委托和路由映射关系，退出
                        })))
                .Build()
                .Run();
        }

        public static async Task RenderHomePageAsync(HttpContext context)
        {
            if (context?.User?.Identity?.IsAuthenticated == true)       //先看看是否存了Authenticated 信息 ，从cookies中找  注释 Determine if this represents the unauthenticated identity
            {
                await context.Response.WriteAsync(                    //href='/Account/Logout'>Sign Out</a>，前后端交互
                    @"<html>
                    <head><title>Index</title></head>
                    <body>" +
                    $"<h3>Welcome {context.User.Identity.Name}</h3>" +
                    @"<a href='/Account/Logout'>Sign Out</a> 
                    </body>
                </html>");
            }
            else
            {
                await context.ChallengeAsync();                     //cookies 里面如果没有的话，这个跳到SignInAsync函数登陆页面
            }
               
        }


        public static async Task SignInAsync(HttpContext context)                //默认先进这个，主页面没有信息    
        {
            if (string.CompareOrdinal(context.Request.Method, "GET") == 0)         //第一次看看get参数是否为空
            {
                await RenderLoginPageAsync(context, null, null, null);             //是空的情况下，跳到登陆页面
            }
            else                                                                   //登陆后，有到这个函数内
            {
                var userName = context.Request.Form["username"];                   //读取cookie
                var password = context.Request.Form["password"];
                if (Accounts.TryGetValue(userName, out var pwd) && pwd == password)   //正常应到数据库中验证
                {
                    var identity = new GenericIdentity(userName, "Passord");         //验证成功，IsAuthenticated==true
                    var principal = new ClaimsPrincipal(identity);                     //这个应该是把identity转换为ClaimsIdentity，添加到List<ClaimsIdentity> 集合中，带有申明的身份对象
                    await context.SignInAsync(principal);                               //context,写入带申明的身份
                }
                else
                {
                    await RenderLoginPageAsync(context, userName, password, "Invalid user name or password!");      //错了就带一条错误信息到登陆页面
                }
            }
        }

        private static Task RenderLoginPageAsync(HttpContext context, string userName, string password,
            string errorMessage)
        {
            context.Response.ContentType = "text/html";
            return context.Response.WriteAsync(              //type='submit' 就是提交
                @"<html>
                <head><title>Login</title></head>
                <body>
                    <form method='post'>" +
                $"<input type='text' name='username' placeholder='User name' value = '{userName}' /> " +
                $"<input type='password' name='password' placeholder='Password' value = '{password}' /> " +
                @"<input type='submit' value='Sign In' />
                    </form>" +
                $"<p style='color:red'>{errorMessage}</p>" +
                @"</body>
            </html>");
        }


        public static async Task SignOutAsync(HttpContext context)
        {
            await context.SignOutAsync();
            context.Response.Redirect("/");                                 //跳转到首页
        }
    }
}