Working with EditorModelEventManager to localise an EditorContentModel powered by /config/lang/*.user.xml files

fr-FR.user.xml

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<language>
  <area alias="tabs">
    <key alias="My Custom Tab">My Custom Tab localized in French!</key>
  </area>
  <area alias="properties">
    <key alias="myCustomProperty">My Custom Property localized in French!</key>
  </area>
  <area alias="propertyDescriptions">    
    <key alias="myCustomProperty">My Custom Property description localized in French!</key>
  </area>
</language>

LocalizedEditorModelEventManagerEventHandler.cs

using System.Collections.Generic;
using System.Globalization;
using Umbraco.Core;
using Umbraco.Core.Services;
using Umbraco.Web;
using Umbraco.Web.Editors;
using Umbraco.Web.Models.ContentEditing;

namespace MyWebsite
{
    public class LocalizedEditorModelEventManagerEventHandler : ApplicationEventHandler
    {
        protected override void ApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
        {
            EditorModelEventManager.SendingContentModel += (sender, args) =>
            {
                var cultureCode = UmbracoContext.Current.Security.CurrentUser.Language;
                var culture = CultureInfo.GetCultureInfo(cultureCode);

                TranslateTabs(args.Model.Tabs, culture, applicationContext.Services.TextService);
                TranslateProperties(args.Model.Properties, culture, applicationContext.Services.TextService);
            };
        }

        private static void TranslateProperties(IEnumerable<ContentPropertyDisplay> properties, CultureInfo culture, ILocalizedTextService textService)
        {
            foreach (var property in properties)
            {
                if (property.HideLabel == false)
                {
                    var localizedLabelValue = textService.Localize("properties/" + property.Alias, culture);
                    if (string.IsNullOrWhiteSpace(localizedLabelValue) == false &&
                        IsDefaultLocalizedValue(localizedLabelValue, property.Alias) == false)
                    {
                        property.Label = localizedLabelValue;
                    }

                    var localizedDescriptionValue = textService.Localize("propertyDescriptions/" + property.Alias,
                        culture);
                    if (string.IsNullOrWhiteSpace(localizedDescriptionValue) == false &&
                        IsDefaultLocalizedValue(localizedDescriptionValue, property.Alias) == false)
                    {
                        property.Description = localizedDescriptionValue;
                    }
                }
            }
        }

        private static void TranslateTabs(IEnumerable<Tab<ContentPropertyDisplay>> tabs, CultureInfo culture, ILocalizedTextService textService)
        {
            foreach (var tab in tabs)
            {
                var localizedValue = textService.Localize("tabs/" + tab.Alias, culture);

                if (string.IsNullOrWhiteSpace(localizedValue) == false && IsDefaultLocalizedValue(localizedValue, tab.Alias) == false)
                {
                    tab.Label = localizedValue;
                }
            }
        }

        private static bool IsDefaultLocalizedValue(string value, string key)
        {
            return string.Equals(value, "[" + key + "]");
        }
    }
}