Added populate lazy-loading extensions.

NzbDrone.Api/Extensions/LazyExtensions.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using NzbDrone.Api.REST;
+using NzbDrone.Common.Cache;
+using NzbDrone.Core.Datastore;
+
+namespace NzbDrone.Api.Extensions
+{
+    public static class LazyExtensions
+    {
+        private static readonly ICached<MethodInfo> SetterCache = new Cached<MethodInfo>();
+
+        public static IEnumerable<TParent> LoadSubtype<TParent, TChild>(this IEnumerable<TParent> parents, Func<TParent, int> foreignKeySelector, IBasicRepository<TChild> childRepository)
+            where TChild : ModelBase, new()
+            where TParent : RestResource
+        {
+            var parentList = parents.Where(p => foreignKeySelector(p) != 0).ToList();
+
+            if (!parentList.Any())
+            {
+                return parents;
+            }
+
+            var ids = parentList.Select(foreignKeySelector).Distinct();
+            var childDictionary = childRepository.Get(ids).ToDictionary(child => child.Id, child => child);
+
+            var childSetter = GetChildSetter<TParent, TChild>();
+
+            foreach (var episode in parentList)
+            {
+                childSetter.Invoke(episode, new object[] { childDictionary[foreignKeySelector(episode)] });
+            }
+
+            return parents;
+        }
+
+
+        private static MethodInfo GetChildSetter<TParent, TChild>()
+            where TChild : ModelBase
+            where TParent : RestResource
+        {
+            var key = typeof(TChild).FullName + typeof(TParent).FullName;
+
+            return SetterCache.Get(key, () =>
+                {
+                    var property = typeof(TParent).GetProperties().Single(c => c.PropertyType == typeof(TChild));
+                    return property.GetSetMethod();
+                });
+        }
+    }
+}