Hi Johan,

I assume you are using dictionary items. We solved this using a webapi handler to intercept the response of the api call and change the doctype name.

WebApiHandler code :

namespace MyApp.WebApiHandlers
{
    using System;
    using System.Globalization;
    using System.Linq;
    using System.Net.Http;    
    using System.Threading.Tasks;
    using System.Web;

    using Umbraco.Core;
    using Umbraco.Core.Dictionary;
    using Umbraco.Core.Logging;
    using Umbraco.Web;
    using Umbraco.Web.Models.ContentEditing;

    internal class ContentGetEmptyHandler : DelegatingHandler
    {
        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            switch (request.RequestUri.AbsolutePath.ToLower())
            {
                case "/umbraco/backoffice/umbracoapi/content/getempty":
                    var userName = HttpContext.Current.User.Identity.Name;
                    return this.SetCorrectDoctypename(request, cancellationToken, userName);
                default:
                    return base.SendAsync(request, cancellationToken);
            }
        }

        private Task<HttpResponseMessage> SetCorrectDoctypename(HttpRequestMessage request, CancellationToken cancellationToken, string userName)
        {
            return base.SendAsync(request, cancellationToken)
                .ContinueWith(task =>
                        {
                            var response = task.Result;
                            try
                            {
                                var queryCollection = request.RequestUri.ParseQueryString();

                                if (queryCollection.AllKeys.Contains("parentId") && queryCollection.AllKeys.Contains("contentTypeAlias")
                                    && queryCollection["parentId"] == "-20")
                                {
                                    // only fiddle with respone when query contains correct parameters and values
                                    // requests from nested content set parent id to -20

                                    // Get the content that we want to modify.
                                    var data = response.Content;
                                    var content = ((ObjectContent)data).Value as ContentItemDisplay;

                                    if (content != null && content.ContentTypeName.StartsWith("#"))
                                    {
                                        // content type name starts with a # so it's probably a dictionary key

                                        // set the culture to the one of the logged in user
                                        var user =
                                            ApplicationContext.Current.Services.UserService.GetByUsername(userName);

                                        Thread.CurrentThread.CurrentCulture = new CultureInfo(user.Language);
                                        Thread.CurrentThread.CurrentUICulture = new CultureInfo(user.Language);

                                        // we don't have umbraco context so we can't use umbracohelper to get the dictionary items
                                        // just use the internal code used by the helper
                                        var factory = CultureDictionaryFactoryResolver.Current.Factory;
                                        var cultureDictionary = factory.CreateDictionary();

                                        var translatedValue = cultureDictionary[content.ContentTypeName.TrimStart('#')];

                                        if (!string.IsNullOrEmpty(translatedValue))
                                        {
                                            content.ContentTypeName = translatedValue;
                                        }
                                     }
                                }                                                             
                            }
                            catch (Exception ex)
                            {
                                LogHelper.Error<ContentGetEmptyHandler>("Could not change the content type name.", ex);
                            }
                            return response;
                    });
        }
    }
}

And you need to register the handler to be used :

    public class Bootstrapper : ApplicationEventHandler
    {

        protected override void ApplicationStarting(
            UmbracoApplicationBase umbracoApplication,
            ApplicationContext applicationContext)
        {            
            GlobalConfiguration.Configuration.MessageHandlers.Add(new ContentGetEmptyHandler());           
        }

}

Dave