BaseController.cs

using System.Globalization;
using System.Threading;
using System.Web.Mvc;

namespace I18nDemo.Controllers
{
    public class BaseController : Controller
    {
        protected override void OnActionExecuting(
            ActionExecutingContext filterContext)
        {
            base.OnActionExecuting(filterContext);

            var cultureInfo = CultureInfo.GetCultureInfo("ar");

            Thread.CurrentThread.CurrentCulture = cultureInfo;
            Thread.CurrentThread.CurrentUICulture = cultureInfo;
        }
    }
}