Add IComparer overload to SortDescription

Author: twsouthwick

Microsoft.Toolkit.Uwp.UI/AdvancedCollectionView/AdvancedCollectionView.cs

@@ -377,24 +377,26 @@ int IComparer<object>.Compare(object x, object y)
 
             foreach (var sd in _sortDescriptions)
             {
-                IComparable cx, cy;
+                object cx, cy;
 
                 if (string.IsNullOrEmpty(sd.PropertyName))
                 {
-                    cx = x as IComparable;
-                    cy = y as IComparable;
+                    cx = x;
+                    cy = y;
                 }
                 else
                 {
                     var pi = _sortProperties[sd.PropertyName];
-                    cx = pi.GetValue(x) as IComparable;
-                    cy = pi.GetValue(y) as IComparable;
+
+                    cx = pi.GetValue(x);
+                    cy = pi.GetValue(y);
                 }
 
                 try
                 {
-                    // ReSharper disable once PossibleUnintendedReferenceComparison
-                    var cmp = cx == cy ? 0 : cx == null ? -1 : cy == null ? +1 : cx.CompareTo(cy);
+                    var comparer = sd.Comparer ?? ComparerAdapter.Instance;
+                    var cmp = comparer.Compare(cx, cy);
+
                     if (cmp != 0)
                     {
                         return sd.Direction == SortDirection.Ascending ? +cmp : -cmp;
@@ -602,5 +604,23 @@ private bool MoveCurrentToIndex(int i)
             OnCurrentChanged(null);
             return true;
         }
+
+        private class ComparerAdapter : IComparer
+        {
+            public static readonly IComparer Instance = new ComparerAdapter();
+
+            private ComparerAdapter()
+            {
+            }
+
+            public int Compare(object x, object y)
+            {
+                var cx = x as IComparable;
+                var cy = y as IComparable;
+
+                // ReSharper disable once PossibleUnintendedReferenceComparison
+                return cx == cy ? 0 : cx == null ? -1 : cy == null ? +1 : cx.CompareTo(cy);
+            }
+        }
     }
 }

Microsoft.Toolkit.Uwp.UI/AdvancedCollectionView/SortDescription.cs

@@ -10,6 +10,8 @@
 // THE CODE OR THE USE OR OTHER DEALINGS IN THE CODE.
 // ******************************************************************
 
+using System.Collections;
+
 namespace Microsoft.Toolkit.Uwp.UI
 {
     /// <summary>
@@ -27,6 +29,11 @@ public class SortDescription
         /// </summary>
         public SortDirection Direction { get; }
 
+        /// <summary>
+        /// Gets the comparer
+        /// </summary>
+        public IComparer Comparer { get; }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="SortDescription"/> class that describes
         /// a sort on the object itself
@@ -37,6 +44,18 @@ public SortDescription(SortDirection direction)
             Direction = direction;
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="SortDescription"/> class that describes
+        /// a sort on the object itself
+        /// </summary>
+        /// <param name="direction">directio of sort</param>
+        /// <param name="comparer">comparer to use</param>
+        public SortDescription(SortDirection direction, IComparer comparer)
+        {
+            Direction = direction;
+            Comparer = comparer;
+        }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="SortDescription"/> class.
         /// </summary>
@@ -47,5 +66,18 @@ public SortDescription(string propertyName, SortDirection direction)
             PropertyName = propertyName;
             Direction = direction;
         }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="SortDescription"/> class.
+        /// </summary>
+        /// <param name="propertyName">name of property to sort on</param>
+        /// <param name="direction">direction of sort</param>
+        /// <param name="comparer">comparer to use</param>
+        public SortDescription(string propertyName, SortDirection direction, IComparer comparer)
+        {
+            PropertyName = propertyName;
+            Direction = direction;
+            Comparer = comparer;
+        }
     }
 }

UnitTests/UI/Test_AdvancedCollectionView.cs

@@ -10,12 +10,15 @@
 // THE CODE OR THE USE OR OTHER DEALINGS IN THE CODE.
 // ******************************************************************
 
+using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Linq;
 using Microsoft.Toolkit.Uwp.UI;
 using Microsoft.VisualStudio.TestPlatform.UnitTestFramework;
 using Microsoft.VisualStudio.TestPlatform.UnitTestFramework.AppContainer;
+
 using Assert = Microsoft.VisualStudio.TestPlatform.UnitTestFramework.Assert;
 
 namespace UnitTests.UI
@@ -229,5 +232,115 @@ public void Test_AdvancedCollectionView_Sorting_OnSelf()
 
             Assert.AreEqual(((Person)a.First()).Age, 42);
         }
+
+        [TestCategory("AdvancedCollectionView")]
+        [UITestMethod]
+        public void Test_AdvancedCollectionView_Sorting_OnSelf_CustomComparable()
+        {
+            var l = new ObservableCollection<Person>
+            {
+                new Person()
+                {
+                    Name = "lorem",
+                    Age = 4
+                },
+                new Person()
+                {
+                    Name = "imsum",
+                    Age = 8
+                },
+                new Person()
+                {
+                    Name = "dolor",
+                    Age = 15
+                },
+                new Person()
+                {
+                    Name = "sit",
+                    Age = 16
+                },
+                new Person()
+                {
+                    Name = "amet",
+                    Age = 23
+                },
+                new Person()
+                {
+                    Name = "consectetur",
+                    Age = 42
+                },
+            };
+
+            var a = new AdvancedCollectionView(l)
+            {
+                SortDescriptions =
+                {
+                    new SortDescription(SortDirection.Ascending, new DelegateComparable((x, y) => -((Person)x).Age.CompareTo(((Person)y).Age)))
+                }
+            };
+
+            Assert.AreEqual(((Person)a.First()).Age, 42);
+        }
+
+        [TestCategory("AdvancedCollectionView")]
+        [UITestMethod]
+        public void Test_AdvancedCollectionView_Sorting_CustomComparable()
+        {
+            var l = new ObservableCollection<Person>
+            {
+                new Person()
+                {
+                    Name = "lorem",
+                    Age = 4
+                },
+                new Person()
+                {
+                    Name = "imsum",
+                    Age = 8
+                },
+                new Person()
+                {
+                    Name = "dolor",
+                    Age = 15
+                },
+                new Person()
+                {
+                    Name = "sit",
+                    Age = 16
+                },
+                new Person()
+                {
+                    Name = "amet",
+                    Age = 23
+                },
+                new Person()
+                {
+                    Name = "consectetur",
+                    Age = 42
+                },
+            };
+
+            var a = new AdvancedCollectionView(l)
+            {
+                SortDescriptions =
+                {
+                    new SortDescription(nameof(Person.Age), SortDirection.Ascending, new DelegateComparable((x, y) => -((int)x).CompareTo((int)y)))
+                }
+            };
+
+            Assert.AreEqual(((Person)a.First()).Age, 42);
+        }
+
+        private class DelegateComparable : IComparer
+        {
+            private Func<object, object, int> _func;
+
+            public DelegateComparable(Func<object, object, int> func)
+            {
+                _func = func;
+            }
+
+            public int Compare(object x, object y) => _func(x, y);
+        }
     }
 }