为什么要使用FluentValidation

1.在日常的开发中，需要验证参数的合理性，不紧前端需要验证传毒的参数，后端也需要验证参数
2.在领域模型中也应该验证,做好防御性的编程是一种好的习惯（其实以前重来不写的，被大佬教育了一番）
3.FluentValidation 是.NET 开发的验证框架，开源,主要是简单好用，内置了一些常用的验证器，可以直接使用，扩展也很方便

使用FluentValidation

1.引入FluentValidation.AspNetCore NuGet包
2.建立需要验证的类

/// <summary>
/// 创建客户
/// </summary>
public class CreateCustomerDto
{
  /// <summary>
  /// 客户姓名
  /// </summary>
  public string CustomerName { get; set; }
  /// <summary>
  /// 客户年龄
  /// </summary>
  public string CustomerAge { get; set; }
  /// <summary>
  /// 客户电话
  /// </summary>
  public string CustomerPhone { get; set; }
  /// <summary>
  /// 客户地址
  /// </summary>
  public Address CustomerAddress { get; set; }
}

/// <summary>
/// 验证
/// </summary>
public class CreateCustomerDtoValidator : AbstractValidator<CreateCustomerDto>
{
  public CreateCustomerDtoValidator()
  {
    RuleFor(x => x.CustomerName)
       .NotEmpty()
       .WithMessage("客户姓名不能为空");
    RuleFor(x => x.CustomerPhone)
       .NotEmpty()
       .WithMessage("客户电话不能为空");

  }
}

3.统一返回验证的信息，ResponseResult为全局统一参数返回的类

  /// <summary>
  /// 添加AddFluentValidationErrorMessage
  /// </summary>
  /// <returns></returns>
  public DependencyInjectionService AddFluentValidationErrorMessage()
  {
    _services.Configure<ApiBehaviorOptions>(options =>
    {
      options.InvalidModelStateResponseFactory = (context) =>
      {
        var errors = context.ModelState
          .Values
          .SelectMany(x => x.Errors
                .Select(p => p.ErrorMessage))
          .ToList();
        var result = new ResponseResult<List<string>>
        {
          StatusCode = "00009",
          Result = errors,
          Message = string.Join(",", errors.Select(e => string.Format("{0}", e)).ToList()),
          IsSucceed = false
        };

        return new BadRequestObjectResult(result);
      };
    });
    return _dependencyInjectionConfiguration;
  }

4.注入验证的类

使用builder.RegisterType().As<IValidator>();比较麻烦每次新增都需要添加一次注入
所以我们使用批量的注入，来减少麻烦,通过反射获取所有的验证的类批量注入

  /// <summary>
  /// 添加MVC
  /// </summary>
  /// <returns></returns>
  public DependencyInjectionService AddMvc()
  {
    _services.AddControllers(options => 
    { 
      options.Filters.Add(typeof(LogHelper));
    }).AddJsonOptions(options =>
    {
      //忽略循环引用
      //options.JsonSerializerOptions.IgnoreReadOnlyProperties = true;
    }).AddFluentValidation(options =>
    {
      options.RunDefaultMvcValidationAfterFluentValidationExecutes = false;
      var validatorList = GetFluentValidationValidator("ConferenceWebApi");
      foreach (var item in validatorList)
      {
        options.RegisterValidatorsFromAssemblyContaining(item);
      }
    });
    return _dependencyInjectionConfiguration;
  }

  /// <summary>
  /// 获取所有的FluentValidation Validator的类
  /// </summary>
  public IEnumerable<Type> GetFluentValidationValidator(string assemblyName)
  {
    if (assemblyName == null)
      throw new ArgumentNullException(nameof(assemblyName));
    if (string.IsNullOrEmpty(assemblyName))
      throw new ArgumentNullException(nameof(assemblyName));

    var implementAssembly = RuntimeHelper.GetAssembly(assemblyName);
    if (implementAssembly == null)
    {
      throw new DllNotFoundException($"the dll ConferenceWebApi not be found");
    }
    var validatorList = implementAssembly.GetTypes().Where(e => e.Name.EndsWith("Validator"));
    return validatorList;
  }