Simplifies the ILocalizedTextService to not have an extension method for null tokens, adds another extension method to accept an array of tokens, adds null checks.

src/Umbraco.Core/Services/LocalizedTextServiceFileSources.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.IO;
+using System.Xml.Linq;
+using Umbraco.Core.Cache;
+
+namespace Umbraco.Core.Services
+{
+    /// <summary>
+    /// Exposes the XDocument sources from files for the default localization text service and ensure caching is taken care of
+    /// </summary>
+    public class LocalizedTextServiceFileSources
+    {
+        private readonly IRuntimeCacheProvider _cache;
+        private readonly DirectoryInfo _fileSourceFolder;
+
+        public LocalizedTextServiceFileSources(IRuntimeCacheProvider cache, DirectoryInfo fileSourceFolder)
+        {
+            if (cache == null) throw new ArgumentNullException("cache");
+            if (fileSourceFolder == null) throw new ArgumentNullException("fileSourceFolder");
+            _cache = cache;
+            _fileSourceFolder = fileSourceFolder;
+        }
+
+        /// <summary>
+        /// returns all xml sources for all culture files found in the folder
+        /// </summary>
+        /// <returns></returns>
+        public IDictionary<CultureInfo, Lazy<XDocument>> GetXmlSources()
+        {
+            var result = new Dictionary<CultureInfo, Lazy<XDocument>>();
+            foreach (var fileInfo in _fileSourceFolder.GetFiles("*.xml"))
+            {
+                var localCopy = fileInfo;
+                var filename = Path.GetFileNameWithoutExtension(localCopy.FullName).Replace("_", "-");
+                var culture = CultureInfo.GetCultureInfo(filename);
+                //get the lazy value from cache                
+                result.Add(culture, new Lazy<XDocument>(() => _cache.GetCacheItem<XDocument>(
+                    string.Format("{0}-{1}", typeof (LocalizedTextServiceFileSources).Name, culture.TwoLetterISOLanguageName), () =>
+                    {
+                        using (var fs = localCopy.OpenRead())
+                        {
+                            return XDocument.Load(fs);
+                        }
+                    }, isSliding: true, timeout: TimeSpan.FromMinutes(10), dependentFiles: new[] {localCopy.FullName})));
+            }
+            return result;
+        }
+    }
+}