Merge pull request #2350 from MediaBrowser/beta

Beta

1 files changed, 84 insertions, 0 deletions

diff --git a/MediaBrowser.Model/Extensions/LinqExtensions.cs b/MediaBrowser.Model/Extensions/LinqExtensions.cs
new file mode 100644
index 000000000..6b2bdb4c7
--- /dev/null
+++ b/MediaBrowser.Model/Extensions/LinqExtensions.cs
@@ -0,0 +1,84 @@
+using System;
+using System.Collections.Generic;
+
+namespace MediaBrowser.Model.Extensions
+{
+    // MoreLINQ - Extensions to LINQ to Objects
+    // Copyright (c) 2008 Jonathan Skeet. All rights reserved.
+    // 
+    // Licensed under the Apache License, Version 2.0 (the "License");
+    // you may not use this file except in compliance with the License.
+    // You may obtain a copy of the License at
+    // 
+    //     http://www.apache.org/licenses/LICENSE-2.0
+    // 
+    // Unless required by applicable law or agreed to in writing, software
+    // distributed under the License is distributed on an "AS IS" BASIS,
+    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+    // See the License for the specific language governing permissions and
+    // limitations under the License.
+
+    public static class LinqExtensions
+    {
+        /// <summary>
+        /// Returns all distinct elements of the given source, where "distinctness"
+        /// is determined via a projection and the default equality comparer for the projected type.
+        /// </summary>
+        /// <remarks>
+        /// This operator uses deferred execution and streams the results, although
+        /// a set of already-seen keys is retained. If a key is seen multiple times,
+        /// only the first element with that key is returned.
+        /// </remarks>
+        /// <typeparam name="TSource">Type of the source sequence</typeparam>
+        /// <typeparam name="TKey">Type of the projected element</typeparam>
+        /// <param name="source">Source sequence</param>
+        /// <param name="keySelector">Projection for determining "distinctness"</param>
+        /// <returns>A sequence consisting of distinct elements from the source sequence,
+        /// comparing them by the specified key projection.</returns>
+
+        public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source,
+            Func<TSource, TKey> keySelector)
+        {
+            return source.DistinctBy(keySelector, null);
+        }
+
+        /// <summary>
+        /// Returns all distinct elements of the given source, where "distinctness"
+        /// is determined via a projection and the specified comparer for the projected type.
+        /// </summary>
+        /// <remarks>
+        /// This operator uses deferred execution and streams the results, although
+        /// a set of already-seen keys is retained. If a key is seen multiple times,
+        /// only the first element with that key is returned.
+        /// </remarks>
+        /// <typeparam name="TSource">Type of the source sequence</typeparam>
+        /// <typeparam name="TKey">Type of the projected element</typeparam>
+        /// <param name="source">Source sequence</param>
+        /// <param name="keySelector">Projection for determining "distinctness"</param>
+        /// <param name="comparer">The equality comparer to use to determine whether or not keys are equal.
+        /// If null, the default equality comparer for <c>TSource</c> is used.</param>
+        /// <returns>A sequence consisting of distinct elements from the source sequence,
+        /// comparing them by the specified key projection.</returns>
+
+        public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source,
+            Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            if (source == null) throw new ArgumentNullException("source");
+            if (keySelector == null) throw new ArgumentNullException("keySelector");
+            return DistinctByImpl(source, keySelector, comparer);
+        }
+
+        private static IEnumerable<TSource> DistinctByImpl<TSource, TKey>(IEnumerable<TSource> source,
+            Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            var knownKeys = new HashSet<TKey>(comparer);
+            foreach (var element in source)
+            {
+                if (knownKeys.Add(keySelector(element)))
+                {
+                    yield return element;
+                }
+            }
+        }
+    }
+}