ASP.NET Web API 数据验证

 // POST api/values
        public HttpResponseMessage Post([FromBody]UserInfo userInfo)
        {
         
            if (string.IsNullOrWhiteSpace(userInfo.Gender))
            {
                ModelState.AddModelError("Gender", "性别不能为空");
            }

            if (ModelState.IsValid)
            {
                // Do something with the product (not shown).
                return new HttpResponseMessage(HttpStatusCode.OK);
            }
            else
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }
        }
public class UserInfo
    {
        public int Id { get; set; }
        [Required]
        [StringLength(20, ErrorMessage = "名字太长了或者太短了", MinimumLength = 4)]
        public string Name { get; set; }

        [RegularExpression(@"([2-5]\d)", ErrorMessage = "年龄在20-50之间")]
        public int Age { get; set; }

        public string Gender { get; set; }
    }

 public class ValidationAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            if (!actionContext.ModelState.IsValid)
            {
                actionContext.Response = actionContext.Request.CreateErrorResponse(
                    HttpStatusCode.BadRequest,
                    actionContext.ModelState);
            }
        }
    }

WebApiConfig.cs

   config.Filters.Add(new ValidationAttribute());