---

前言

FluentValidation 是一个流行的 .NET 库，用于构建强类型的验证规则。它通常用于验证领域模型、DTO等对象。
注意：在ASP.NET Core中，我们可以使用FluentValidation.AspNetCore包来更好地集成，它提供了自动验证的功能，这样我们就不需要在每个Action中手动调用验证了。

一、使用步骤

1.安装 NuGet 包

1. 执行命令

   Install-Package FluentValidation.AspNetCore
   

2.创建模型

1. UserRequest.cs

   namespace HostedService.Entity.ResOrReqEntity
   {
       public class UserRequest
       {
           public long Id { get; set; }
   
           public string UserName { get; set; }
           public string Email {  get; set; }
   
           public string Password { get; set; }
   
           public string PasswordAgain {  get; set; }
       }
   }
   

3.创建验证器

1. UserRequestValidate.cs

   using FluentValidation;
   using HostedService.Entity;
   using HostedService.Entity.ResOrReqEntity;
   using Microsoft.AspNetCore.Http.HttpResults;
   using Microsoft.AspNetCore.Identity;
   using Microsoft.AspNetCore.Mvc;
   
   namespace HostedService.ValidateService
   {
       public class UserRequestValidate : AbstractValidator<UserRequest>
       {
           private readonly UserManager<User> _user;
           public UserRequestValidate(UserManager<User> user)
           {
               _user= user;      
   
               RuleFor(x => x.Email).NotNull().EmailAddress()
                   .WithMessage("邮箱不合法")
                   .Must(x => x.EndsWith("@163.com") || x.EndsWith("@qq.com"))
                   .WithMessage("邮箱只支持163或QQ邮箱");
               RuleFor(x => x.UserName).NotNull().Length(3, 10)
                   .WithMessage("用户名长度需要为3-10个")
                   .MustAsync(FindUserByNameAsync)
                   //.MustAsync(async (x, _) => await user.FindByNameAsync(x) == null)
                   .WithMessage("用户已存在");
   
               RuleFor(x => x.Password).Equal(x => x.PasswordAgain)
                   .WithMessage("两次输入的密码必须一致");
   
           }
           private async Task<bool> FindUserByNameAsync(string name, CancellationToken  token)
           {
               var res=await _user.FindByNameAsync(name);
               return res == null;
           }
       }
   }
   
   

4.配置 Program.cs

1. Program.cs

 // 注册验证器（使用异步支持）
builder.Services.AddValidatorsFromAssemblyContaining<Program>(ServiceLifetime.Scoped);
// 自定义验证错误响应
builder.Services.Configure<ApiBehaviorOptions>(options =>
{
    options.InvalidModelStateResponseFactory = context =>
    {
        var errors = context.ModelState
            .Where(e => e.Value.Errors.Count > 0)
            .ToDictionary(
                kvp => kvp.Key,
                kvp => kvp.Value.Errors.Select(e => e.ErrorMessage).ToArray()
            );

        return new BadRequestObjectResult(new
        {
            Status = 400,
            Message = "Validation failed",
            Errors = errors
        });
    };
});

5.创建控制器

1. TestController.cs

   using HostedService.Entity;
   using HostedService.Entity.ResOrReqEntity;
   using Microsoft.AspNetCore.Http;
   using Microsoft.AspNetCore.Identity;
   using Microsoft.AspNetCore.Mvc;
   
   namespace HostedService.Controllers
   {
       [Route("api/[controller]/[action]")]
       [ApiController]
       public class TestController : ControllerBase
       {
           private readonly UserManager<User> _userManager;
           private readonly RoleManager<Role> _roleManager;
           private readonly IWebHostEnvironment _webHostEnvironment;
   
           public TestController(UserManager<User> userManager, RoleManager<Role> roleManager, IWebHostEnvironment webHostEnvironment)
           {
               _userManager = userManager;
               _roleManager = roleManager;
               _webHostEnvironment = webHostEnvironment;
           }
           
                [HttpPost]
   	     public async Task<IActionResult> Add(UserRequest userRequest, [FromServices] IValidator<UserRequest> validator)
   	     {
   	     	 //手动出发验证
   	         var validateRes =await validator.ValidateAsync(userRequest);
   	         if (!validateRes.IsValid)
   	         {
   	             return BadRequest(validateRes.ToDictionary());
   	         }
   	         User user = new User { UserName = userRequest.UserName, Email = userRequest.Email };
   	         await _userManager.CreateAsync(user, userRequest.Password);
   	         return Ok();
   	     }
       }
   }
   

6.测试结果

1. 示例
   UserRequest

   {
     "id": 0,
     "userName": "LGF",
     "email": "1231231@gmail.com",
     "password": "123ggg",
     "passwordAgain": "123gg"
   }
   

   Response Body

   Error: response status is 400
   
   Response body
   {
     "Email": [
       "邮箱只支持163或QQ邮箱"
     ],
     "UserName": [
       "用户已存在"
     ],
     "Password": [
       "两次输入的密码必须一致"
     ]
   }
   

二、常见问题及注意事项

• 验证器未触发
  • 确保 AddFluentValidation() 在 AddControllers() 之后调用
  • 检查验证器是否在注册的程序集中
• 生命周期管理
  • 验证器建议注册为 Scoped 生命周期
  • 异步验证中注入的仓储需支持异步操作
• 混合验证规则优先级

  RuleFor(x => x.UserName).NotNull().Length(3, 10) //同步验证
  .WithMessage("用户名长度需要为3-10个")
  .MustAsync(FindUserByNameAsync)//异步验证
  .WithMessage("用户已存在");
  

三、性能优化建议

• 同步验证优先原则：将轻量级验证（如格式校验）放在同步阶段
• 异步验证批处理：对需要访问外部资源的验证进行合并查询
• 验证缓存机制：对高频静态数据（如行政区划）可添加内存缓存

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总结

通过以上配置，您可以在 ASP.NET Core 8.0 Web API 中实现验证逻辑，保持控制器简洁并返回结构化的错误响应。