kreta/Kreta.WebApi/User/Kreta.User.WebApi/App_Start/Startup.cs

using System;
using System.Configuration;
using System.Web.Configuration;
using System.Web.Http;
using Microsoft.Owin;
using Owin;

[assembly: OwinStartup(typeof(Kreta.User.WebApi.App_Start.Startup))]
namespace Kreta.User.WebApi.App_Start
{
    public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            GlobalConfiguration.Configure(WebApiConfig.Register);

            IncludeErrorDetailPolicy errorDetailPolicy;

            var customErrors = (CustomErrorsSection)ConfigurationManager.GetSection("system.web/customErrors");
            switch (customErrors.Mode)
            {
                case CustomErrorsMode.RemoteOnly:
                    errorDetailPolicy = IncludeErrorDetailPolicy.LocalOnly;
                    break;
                case CustomErrorsMode.On:
                    errorDetailPolicy = IncludeErrorDetailPolicy.Never;
                    break;
                case CustomErrorsMode.Off:
                    errorDetailPolicy = IncludeErrorDetailPolicy.Always;
                    break;
                default:
                    throw new ArgumentOutOfRangeException();
            }

            log4net.Config.XmlConfigurator.Configure();

            var config = GlobalConfiguration.Configuration;
            config.IncludeErrorDetailPolicy = errorDetailPolicy;

            app.UseWebApi(config);
        }
    }
}