ASP.NET Web API: model is valid if error message is set from resources

Question

The problem is that in ApiController ModelState.IsValid is always true if I use .rsx file (Resources) to provide custom error message.

Here is my model:

public class LoginModel
{
    public string Email { get; set; }

    [Required]
    [MinLength(5)]
    public string Password { get; set; }
}

Method in ApiController:

    [HttpPost]
    [ModelValidationFilter]
    public void Post(LoginModel model)
    {
        var a = ModelState.IsValid;
    }

And the filter:

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

I'm sending this in POST request:

{ Email: "[email protected]", Password: "a" }

ModelState.IsValid is false and the response is as expected:

{
   "Message": "The request is invalid.",
   "ModelState":
   {
       "model.Password":
       [
           "The field Password must be a string or array type with a minimum length of '5'."
       ]
   }
}

But if I use the resources (configured as Public and Embedded Resource build action) in validation attributes:

public class LoginModel
{
    public string Email { get; set; }

    [Required]
    [MinLength(5, ErrorMessageResourceName = "Test", ErrorMessageResourceType = typeof(Resources.Localization))]
    public string Password { get; set; }
}

('Test' key holds just 'Test' string value) ModelState.IsValid is true.

Resources class is visible, and resharper correctly validates string provided in ErrorMessageResourceName.

Answer 1

I tried your solution, yet I do not understand class Resources.Localization. Where did it come from? My solution is described below and it was working with good resources.

Model:

using TestApp.Properties;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;

namespace TestApp.Models
{
    public class LoginModel
    {
        public string Email { get; set; }
        [Required]
        [MinLength(5, ErrorMessageResourceName="Test", ErrorMessageResourceType=typeof(Resources))]
        public string Password { get; set; }
    }
}

ModelValidationFilterAttribute:

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

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

Two resource files, one general Resources.resx, containing string key/value Test/something; the other one Resources.de-DE.resx, containing string key/value Test/something_DE.

Using fiddler I sent this:

Header:
User-Agent: Fiddler
Host: localhost:63315
Content-Length: 37
Content-Type: application/json

Body:

{Email:"[email protected]", Password:"a"}

Response was string:

HTTP/1.1 400 Bad Request
Cache-Control: no-cache
Pragma: no-cache
Content-Type: application/json; charset=utf-8
Expires: -1
Server: Microsoft-IIS/8.0
X-AspNet-Version: 4.0.30319
X-SourceFiles: =?UTF-8?B?RDpcV29ya1xDU1xGYkJpcnRoZGF5QXBwXEZiQmRheUFwcDJcYXBpXGxvZ2lu?=
X-Powered-By: ASP.NET
Date: Fri, 28 Jun 2013 14:56:54 GMT
Content-Length: 83

{"Message":"The request is invalid.","ModelState":{"model.Password":["something"]}}

For de-DE, request header was:

User-Agent: Fiddler
Host: localhost:63315
Content-Length: 37
Accept-Language: de-DE
Content-Type: application/json

Response was:

HTTP/1.1 400 Bad Request
Cache-Control: no-cache
Pragma: no-cache
Content-Type: application/json; charset=utf-8
Expires: -1
Server: Microsoft-IIS/8.0
X-AspNet-Version: 4.0.30319
X-SourceFiles: =?UTF-8?B?RDpcV29ya1xDU1xGYkJpcnRoZGF5QXBwXEZiQmRheUFwcDJcYXBpXGxvZ2lu?=
X-Powered-By: ASP.NET
Date: Fri, 28 Jun 2013 14:57:39 GMT
Content-Length: 86

{"Message":"The request is invalid.","ModelState":{"model.Password":["something_DE"]}}

As you can see, message was with "_DE" as it was read from localized resources file.

Is this something that you wanted to achieve?

Kind regards.

Edit: route configuration was

config.Routes.MapHttpRoute(
          name: "LoginRoute",
          routeTemplate: "api/login",
          defaults: new { controller = "Login", action = "PostLogin" },
          constraints: new { httpMethod = new HttpMethodConstraint(HttpMethod.Post) }
          );

Web.config had next section added:

<system.web>
...
        <globalization culture="auto" uiCulture="auto" />
...
</system.web>