ValidateParametersAttribute.cs

ValidateParametersAttribute.cs

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

using static AttributeTargets;

[AttributeUsage(Class | Method, Inherited = true, AllowMultiple = false)]
public class ValidateParametersAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(HttpActionContext context)
    {
        foreach (HttpParameterBinding binding in
            context.ActionDescriptor.ActionBinding.ParameterBindings)
        {
            HttpParameterDescriptor parameter = binding.Descriptor;

            IEnumerable<ValidationAttribute> validations =
                parameter.GetCustomAttributes<ValidationAttribute>() ??
                Enumerable.Empty<ValidationAttribute>();

            if (false == validations.Any())
                continue;

            string name = parameter.ParameterName;
            object value = context.ActionArguments[name];
            try
            {
                if (value == null)
                {
                    foreach (ValidationAttribute v in validations)
                        v.Validate(value, name);
                }
                else
                {
                    var validationContext = new ValidationContext(value);
                    foreach (ValidationAttribute v in validations)
                        v.Validate(value, validationContext);
                }
            }
            catch (ValidationException exception)
            {
                context.Response = context.Request.CreateErrorResponse(
                    HttpStatusCode.BadRequest, exception.Message);
                break;
            }
        }
    }
}