public class validationActionFilter:ActionFilterAttribute

    {

        public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)

        {

            var modelState = actionContext.ModelState;

            if(!modelState.IsValid)

            {

                dynamic errors = new JObject ( );

                foreach(var key in modelState.Keys)

                {

                    var state = modelState[key];

                    if(state.Errors.Any ( ))

                    {

                        errors[key] = state.Errors.First ( ).ErrorMessage;

                    }

                }

                actionContext.Response = new HttpResponseMessage ( HttpStatusCode.BadRequest )

                {

                    Content = new StringContent ( Convert.ToString ( errors ) )

                };

            }

        }

    }

public class ValidationActionFilter : ActionFilterAttribute

    {

        public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)

        {

            var modelState = actionContext.ModelState;

            if (!modelState.IsValid)

            {

                ApiResult result = new ApiResult();

                result.code = ApiResultCode.fail;

                result.msg = "输入数据验证失败";

                //找到出错的字段以及出错信息

                var errorFieldsAndMsgs = modelState.Where(m => m.Value.Errors.Any())

                    .Select(x => new { x.Key, x.Value.Errors });

                result.desc = string.Join(",", errorFieldsAndMsgs.SelectMany(p => p.Errors.Select(t => t.ErrorMessage)).ToArray());

                actionContext.Response = new HttpResponseMessage(HttpStatusCode.BadRequest)

                {

                    Content = new StringContent(JsonConvert.SerializeObject(result))

                };

            }

        }

public class ValidationActionFilter : ActionFilterAttribute

    {

        public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)

        {

            var modelState = actionContext.ModelState;

            if (!modelState.IsValid)

            {

                ApiResult result = new ApiResult();

                result.code = ApiResultCode.fail;

                result.msg = "输入数据验证失败";

                //找到出错的字段以及出错信息

                var errorFieldsAndMsgs = modelState.Where(m => m.Value.Errors.Any())

                    .Select(x => new { x.Key, x.Value.Errors });

                result.desc = string.Join(",", errorFieldsAndMsgs.SelectMany(p => p.Errors.Select(t => t.ErrorMessage)).ToArray());

                actionContext.Response = new HttpResponseMessage(HttpStatusCode.BadRequest)

                {

                    Content = new StringContent(JsonConvert.SerializeObject(result))

                };

            }

        }