Model Validation in ASP.NET Web API By Mike Wasson|July 20, 2012 268 of 294 people found this helpful

using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http.Controllers;
using System.Web.Http.Filters;
using System.Web.Http.ModelBinding;

namespace MyApi.Filters
{
public class ValidateModelAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(HttpActionContext actionContext)
{
if (actionContext.ModelState.IsValid == false)
{
actionContext.Response = actionContext.Request.CreateErrorResponse(
HttpStatusCode.BadRequest, actionContext.ModelState);
}
}
}
}

　　Corresponding result pasted below:

HTTP/1.1 400 Bad Request
Content-Type: application/json; charset=utf-8
Date: Tue, 16 Jul 2013 21:02:29 GMT
Content-Length: 331

{
"Message": "The request is invalid.",
"ModelState": {
"product": [
"Required property 'Name' not found in JSON. Path '', line 1, position 17."
],
"product.Name": [
"The Name field is required."
],
"product.Weight": [
"The field Weight must be between 0 and 999."
]
}
}

　　Pasted below exception the link, global exception handling in webapi