Add ToSortedCollection() operator for ObservableCache and ObservableList

DynamicData.Tests/Cache/ToSortedCollectionFixture.cs

@@ -0,0 +1,105 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reactive.Disposables;
+using System.Reactive.Linq;
+using DynamicData.Binding;
+using DynamicData.Tests.Domain;
+using FluentAssertions;
+using Microsoft.Reactive.Testing;
+using Xunit;
+
+namespace DynamicData.Tests.Cache
+{
+    public class ToSortedCollectionFixture : IDisposable
+    {
+        private readonly SourceCache<Person, int> _cache;
+        private readonly List<Person> _sortedCollection = new List<Person>();
+        private readonly List<Person> _unsortedCollection = new List<Person>();
+        private readonly CompositeDisposable _cleanup = new CompositeDisposable();
+
+        public ToSortedCollectionFixture()
+        {
+            _cache = new SourceCache<Person, int>(p => p.Age);
+            _cache.AddOrUpdate(Enumerable.Range(1, 10).Select(i => new Person("Name" + i, i)).ToArray());
+        }
+
+        public void Dispose()
+        {
+            _cache.Dispose();
+            _cleanup.Dispose();
+        }
+
+        [Fact]
+        public void SortAscending()
+        {
+            TestScheduler testScheduler = new TestScheduler();
+
+            _cleanup.Add(_cache.Connect()
+                .ObserveOn(testScheduler)
+                .Sort(SortExpressionComparer<Person>.Ascending(p => p.Age))
+                .ToCollection()
+                .Do(persons =>
+                {
+                    _unsortedCollection.Clear();
+                    _unsortedCollection.AddRange(persons);
+                })
+                .Subscribe());
+
+            _cleanup.Add(_cache.Connect()
+                .ObserveOn(testScheduler)
+                .ToSortedCollection(p => p.Age)
+                .Do(persons =>
+                {
+                    _sortedCollection.Clear();
+                    _sortedCollection.AddRange(persons);
+                })
+                .Subscribe());
+
+            // Insert an item with a lower sort order
+            _cache.AddOrUpdate(new Person("Name", 0));
+
+            testScheduler.AdvanceBy(TimeSpan.FromSeconds(2).Ticks);
+
+            _cache.Items.Should().Equal(_unsortedCollection);
+            _cache.Items.Should().NotEqual(_sortedCollection);
+            _cache.Items.OrderBy(p => p.Age).Should().Equal(_sortedCollection);
+        }
+
+        [Fact]
+        public void SortDescending()
+        {
+            TestScheduler testScheduler = new TestScheduler();
+
+            _cleanup.Add(_cache.Connect()
+                .ObserveOn(testScheduler)
+                .Sort(SortExpressionComparer<Person>.Ascending(p => p.Age))
+                .ToCollection()
+                .Do(persons =>
+                {
+                    _unsortedCollection.Clear();
+                    _unsortedCollection.AddRange(persons);
+                })
+                .Subscribe());
+
+            _cleanup.Add(_cache.Connect()
+                .ObserveOn(testScheduler)
+                .ToSortedCollection(p => p.Age, SortDirection.Descending)
+                .Do(persons =>
+                {
+                    _sortedCollection.Clear();
+                    _sortedCollection.AddRange(persons);
+                })
+                .Subscribe());
+
+            // Insert an item with a lower sort order
+            _cache.AddOrUpdate(new Person("Name", 0));
+
+            testScheduler.AdvanceBy(TimeSpan.FromSeconds(2).Ticks);
+
+            _cache.Items.Should().Equal(_unsortedCollection);
+            _cache.Items.Should().NotEqual(_sortedCollection);
+            _cache.Items.OrderByDescending(p => p.Age).Should().Equal(_sortedCollection);
+        }
+    }
+}

DynamicData/Cache/ObservableCacheEx.cs

@@ -1199,6 +1199,43 @@ public static IObservable<IReadOnlyCollection<TObject>> ToCollection<TObject, TK
         {
             return source.QueryWhenChanged(query => new ReadOnlyCollectionLight<TObject>(query.Items));
         }
+
+        /// <summary>
+        /// Converts the changeset into a fully formed sorted collection. Each change in the source results in a new sorted collection
+        /// </summary>
+        /// <typeparam name="TObject">The type of the object.</typeparam>
+        /// <typeparam name="TKey">The type of the key.</typeparam>
+        /// <typeparam name="TSortKey">The sort key</typeparam>
+        /// <param name="source">The source.</param>
+        /// <param name="sort">The sort function</param>
+        /// <param name="sortOrder">The sort order. Defaults to ascending</param>
+        /// <returns></returns>
+        public static IObservable<IReadOnlyCollection<TObject>> ToSortedCollection<TObject, TKey, TSortKey>(this IObservable<IChangeSet<TObject, TKey>> source, 
+            Func<TObject, TSortKey> sort, SortDirection sortOrder = SortDirection.Ascending)
+        {
+            return source.QueryWhenChanged(query => sortOrder == SortDirection.Ascending 
+                ? new ReadOnlyCollectionLight<TObject>(query.Items.OrderBy(sort)) 
+                : new ReadOnlyCollectionLight<TObject>(query.Items.OrderByDescending(sort)));
+        }
+
+        /// <summary>
+        /// Converts the changeset into a fully formed sorted collection. Each change in the source results in a new sorted collection
+        /// </summary>
+        /// <typeparam name="TObject">The type of the object.</typeparam>
+        /// <typeparam name="TKey">The type of the key.</typeparam>
+        /// <param name="source">The source.</param>
+        /// <param name="comparer">The sort comparer</param>
+        /// <returns></returns>
+        public static IObservable<IReadOnlyCollection<TObject>> ToSortedCollection<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source,
+            IComparer<TObject> comparer)
+        {
+            return source.QueryWhenChanged(query =>
+            {
+                var items = query.Items.AsList();
+                items.Sort(comparer);
+                return new ReadOnlyCollectionLight<TObject>(items);
+            });
+        }
 
         #endregion