.NET高级技术 - 使用.NET实现简单登录功能 - 《小羊的图书馆》

用户登录：输入账号和密码，然后判断用户名和密码是否正确，返回对应的处理结果登录以后将用户名和密码存放在Session中并在跳转后的页面上从Session中读取用户名和密码，并显示在界面上

定义接口入参 ```csharp namespace WebApplication5.DTO { public class UserLoginDTO {

 public string? username { get; set; }
 public string? password { get; set; }
 public override string ToString(){
     return "username: " + username + " password: " + password;
 }

} }


2. 定义统一JSON返回格式
```csharp
namespace WebApplication5.DTO
{
    public class Result
    {
        public Result() { }
        public Result(int code,string message, Object result) 
        {
            this.code = code;
            this.message = message;
            this.result = result;
        }
        public Result(int code,string message){
            this.code = code;
            this.message = message;
        }
        public static Result Success(string message)
        {
            return new Result(200,message);
        }
        public static Result Success(string message, Object data)
        {
            return new Result(200, message, data);
        }
        public static Result Error(string message)
        {
            return new Result(500, message);
        }
        public int code { get; set; }
        public string? message { get; set; }
        public object? result { get; set; }
        public override string ToString()
        {
            return "code: " + code + " message: " + message + " result: " + result;
        }
    }
}

定义登录控制器UserController
这里为了顺应老师作业的要求，用户名和密码是随便填写的实际上如果要进行校验
1. 有数据库 => 执行SQL语句进行判断账号密码是否正确
2. 无数据库 => 结合代码判断账号和密码是否正确
对入参进行参数校验，然后将返回结果使用JsonResult包裹进行返回

using Microsoft.AspNetCore.Mvc;
using WebApplication5.DTO;
namespace WebApplication5.controllers;
[ApiController]
[Route("[controller]")]
public class UserLoginController : ControllerBase
{
    private readonly ILogger<UserLoginController> _logger;
    public UserLoginController(ILogger<UserLoginController> logger)
    {
        _logger = logger;
    }
    [HttpPost(Name = "UserLogin")]
    public JsonResult doLogin([FromBody] UserLoginDTO userLoginDTO)
    {
        Console.WriteLine("当前登录用户信息" + userLoginDTO.ToString());
        Console.WriteLine("login success");
        if(userLoginDTO.username == null && userLoginDTO.password == null){
            return new JsonResult(Result.Error("username and password cannot be null"));
        }
        if(userLoginDTO.username == null){
            return new JsonResult(Result.Error("username cannot be null"));
        }
        if(userLoginDTO.password == null){
            return new JsonResult(Result.Error("password cannot be null"));
        }
        HttpContext.Session.SetString("username", userLoginDTO.username);
        HttpContext.Session.SetString("password", userLoginDTO.password);
        return new JsonResult(Result.Success("login success"));
    }
}

在前端页面使用Ajax发起请求 ```csharp @page @model IndexModel @{ ViewData[“Title”] = “首页”; } <!DOCTYPE html>


5. 登录跳转后的页面
```csharp
@page
@model WebApplication5.Pages.HomeModel
@{
    ViewData["Title"] = "页面2";
    string? username = this.ViewContext.HttpContext.Session.GetString("username");
    string? password = this.ViewContext.HttpContext.Session.GetString("password");
    if(username != null && password != null){
        <text>用户名: @username</text>
        <text>密码：@password</text>
    }else{
        <text>请先登录</text>
        this.ViewContext.HttpContext.Response.Redirect("/");
    }
}
<!DOCTYPE html>
<html lang="zh-cn">
<head>
    <meta charset="utf-8" />
    <style>
        .pb-3{
            font-size: 40pt;
            color: blue;
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>
<script type="text/javascript">
</script>

从页面的请求路径中获取参数在ASP.NET下，可以通过Request.QueryString[“id”] 来获取传入的参数，但是在 ASP.NET Core 下是会报错的需要改为： HttpContext.Request.Query[“id”] 来获取

@page
@model WebApplication5.Pages.AboutModel
@{
    ViewData["Title"] = "页面3";
    string username = HttpContext.Request.Query["username"];
    string password = HttpContext.Request.Query["password"];
    if(username != null && password != null){
        <text>用户名: @username</text>
        <text>密码：@password</text>
    }else{
        <text>请先登录</text>
        this.ViewContext.HttpContext.Response.Redirect("/");
    }
}
<!DOCTYPE html>
<html lang="zh-cn">
<head>
    <meta charset="utf-8" />
    <style>
        .pb-3{
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 40pt;
            color: blue;
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>
<script type="text/javascript">
</script>