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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": "[e-mail]","password": "123ggg","passwordAgain": "123gg"
   }
   

   Response Body

   Error: response status is 400Response 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。