Moved Extension methods in common to subfolder

src/NzbDrone.Common/Extensions/IEnumerableExtensions.cs

@@ -0,0 +1,41 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace NzbDrone.Common.Extensions
+{
+    public static class EnumerableExtensions
+    {
+        public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
+        {
+            var knownKeys = new HashSet<TKey>();
+
+            return source.Where(element => knownKeys.Add(keySelector(element)));
+        }
+
+        public static void AddIfNotNull<TSource>(this List<TSource> source, TSource item)
+        {
+            if (item == null)
+            {
+                return;
+            }
+
+            source.Add(item);
+        }
+
+        public static bool Empty<TSource>(this IEnumerable<TSource> source)
+        {
+            return !source.Any();
+        }
+
+        public static bool None<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+        {
+            return !source.Any(predicate);
+        }
+
+        public static bool NotAll<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+        {
+            return !source.All(predicate);
+        }
+    }
+}