我需要在 ASP.Net core Web API 的验证属性中返回自定义的验证结果（响应）

我需要在 ASP.Net core Web API 中返回自定义的验证结果（响应）失效属性 这是我创建的 ValidationAttribute。

class MaxResultsAttribute : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        int maxResults = (int)value;

        if (maxResults <= 0)
        {
            return new CustomValidationResult(new ValidationResult("MaxResults should be greater than 0"));
        }

        return ValidationResult.Success;
    }
}

我创建了继承 ValidationResult 的 CustomValidationResult 对象，以便我可以返回我自己的自定义响应：

public class CustomValidationResult : ValidationResult
{
    public int FaultCode { get; set; }

    public string FaultMessage { get; set; }

    public CustomValidationResult(ValidationResult validationResult) : base(validationResult)
    {
        FaultCode = 123;
        FaultMessage = validationResult.ErrorMessage;
    }
}

但这不起作用 我需要返回我自己的错误响应

实际反应：

    {
      "MaxResults": [
        "MaxResults should be greater than 0"
      ] 
    }

我期待的回应：

    {
      "code": "55",
      "message": "The following validation errors occurred: MaxResults should be greater than 0"
    }

我期待的回应：

{
  "code": "55",
  "message": "The following validation errors occurred: MaxResults should be greater than 0"
}

我已经使用您的代码重现了问题，使用 CustomValidationResult，我只能得到像您一样的实际响应。为了实现上述行为，作为解决方法，我建议您可以尝试使用操作过滤器来处理验证失败错误响应。检查以下示例代码：

1. 创建包含返回字段的自定义 ValidationError 模型：

    public class ValidationError
    {
        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
        public string Field { get; }
   
        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
        public int Code { get; set; }
   
        public string Message { get; }
   
        public ValidationError(string field,int code, string message)
        {
            Field = field != string.Empty ? field : null;
            Code = code != 0 ? code : 55;
            Message = message;
        }
    }
   
    public class ValidationResultModel
    {
        public string Message { get; }
   
        public List<ValidationError> Errors { get; }
   
        public ValidationResultModel(ModelStateDictionary modelState)
        {
            Message = "Validation Failed";
            Errors = modelState.Keys
                    .SelectMany(key => modelState[key].Errors.Select(x => new ValidationError(key,0, x.ErrorMessage)))
                    .ToList();
        }
    }
   

2. 创建自定义 IActionResult。默认情况下，当显示验证错误时，会返回BadRequestObjectResult，HTTP状态代码为400。这里我们可以更改Http状态代码。

    public class ValidationFailedResult : ObjectResult
    {
        public ValidationFailedResult(ModelStateDictionary modelState)
            : base(new ValidationResultModel(modelState))
        {
            StatusCode = StatusCodes.Status422UnprocessableEntity; //change the http status code to 422.
        }
    }
   

3. 创建自定义操作过滤器属性：

    public class ValidateModelAttribute: ActionFilterAttribute
    { 
        public override void OnActionExecuting(ActionExecutingContext context)
        {
            if (!context.ModelState.IsValid)
            {
                context.Result = new ValidationFailedResult(context.ModelState);
            }
        }
    }
   

4. 在 Startup.ConfigureServices 中将默认响应类型更改为 SerializedError：

        services.AddControllers().ConfigureApiBehaviorOptions(options =>
        {
            options.InvalidModelStateResponseFactory = context =>
            {
                var result = new ValidationFailedResult(context.ModelState);
   
                // TODO: add `using System.Net.Mime;` to resolve MediaTypeNames
                result.ContentTypes.Add(MediaTypeNames.Application.Json);
                result.ContentTypes.Add(MediaTypeNames.Application.Xml);
   
                return result;
            };
        });
   

5. 在操作方法或控制器中添加自定义操作过滤器。

    [HttpPost]
    [ValidateModel]
    public async Task<ActionResult<Student>> PostStudent(Student student)
    { 
       ...
    }
   

6. 创建具有自定义属性验证的 Student 模型（Min18Years）：

    public class Student
    {
        [Key]
        public int Id { get; set; }
   
        [Required(ErrorMessage = "Please enter name")]
        public string Name { get; set; }
   
        [Required(ErrorMessage = "Please choose admission date.")]
        [Display(Name = "Admission Date")]
        [DataType(DataType.Date)] 
        public DateTime AdmissionDate { get; set; }
   
        [Display(Name = "Date of Birth")]
        [DataType(DataType.Date)]
        [Min18Years]
        public DateTime DateofBirth { get; set; }
    }
   
   
    public class Min18Years : ValidationAttribute
    {
        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            var student = (Student)validationContext.ObjectInstance;
   
            if (student.DateofBirth == null)
                return new ValidationResult("Date of Birth is required.");
   
            var age = DateTime.Today.Year - student.DateofBirth.Year;
   
            if (age <= 0)
            { 
                return new ValidationResult("MaxResults should be greater than 0");
            } 
            return (age >= 18)
                ? ValidationResult.Success
                : new ValidationResult("Student should be at least 18 years old.");
        }
    }  
   

运行应用程序后，结果如下：

参考：

处理 ASP.NET Core Web API 中的验证失败错误

处理 ASP.NET Core Web API 的验证响应