.Net Core3.0 WEB API 中使用FluentValidation验证，实现批量注入

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>();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;
    }

5.使用起来就十分简单了

    /// <summary>
    /// 创建客户
    /// </summary>
    /// <param name="input"></param>
    /// <returns></returns>
    [HttpPost]
    public async Task<ResponseResult<string>> CreateCustomer([FromBody] CreateCustomerDto input)
    {
        var createCustomerCommand = new CreateCustomerCommand(input.CustomerName,input.CustomerAge,input.CustomerPhone,input.CustomerAddress);
        await _commandService.SendCommandAsync(createCustomerCommand);
        var result = new ResponseResult<string>
        {
            IsSucceed = true,
            Result = "创建客户成功！"
        };
        return result;
    }

FluentValidation学习的资料

感谢大佬们的分享，零度编程中的教程非常的全面，包括了许多的验证器的使用，记不住时直接可以翻阅查看
零度编程：https://www.xcode.me/post/5849
Lamond Lu：https://www.cnblogs.com/lwqlun/p/10311945.html