Move comparer into SortDescription

This way the Comparer property on SortDescription is never null

Author: twsouthwick

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

@@ -394,8 +394,7 @@ int IComparer<object>.Compare(object x, object y)
 
                 try
                 {
-                    var comparer = sd.Comparer ?? ComparerAdapter.Instance;
-                    var cmp = comparer.Compare(cx, cy);
+                    var cmp = sd.Comparer.Compare(cx, cy);
 
                     if (cmp != 0)
                     {
@@ -604,23 +603,5 @@ 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 +10,7 @@
 // THE CODE OR THE USE OR OTHER DEALINGS IN THE CODE.
 // ******************************************************************
 
+using System;
 using System.Collections;
 
 namespace Microsoft.Toolkit.Uwp.UI
@@ -40,8 +41,8 @@ public class SortDescription
         /// </summary>
         /// <param name="direction">direction of sort</param>
         public SortDescription(SortDirection direction)
+            : this(null, direction, ObjectComparer.Instance)
         {
-            Direction = direction;
         }
 
         /// <summary>
@@ -51,9 +52,8 @@ public SortDescription(SortDirection direction)
         /// <param name="direction">directio of sort</param>
         /// <param name="comparer">comparer to use</param>
         public SortDescription(SortDirection direction, IComparer comparer)
+            : this(null, direction, comparer)
         {
-            Direction = direction;
-            Comparer = comparer;
         }
 
         /// <summary>
@@ -62,9 +62,8 @@ public SortDescription(SortDirection direction, IComparer comparer)
         /// <param name="propertyName">name of property to sort on</param>
         /// <param name="direction">direction of sort</param>
         public SortDescription(string propertyName, SortDirection direction)
+            : this(propertyName, direction, ObjectComparer.Instance)
         {
-            PropertyName = propertyName;
-            Direction = direction;
         }
 
         /// <summary>
@@ -79,5 +78,23 @@ public SortDescription(string propertyName, SortDirection direction, IComparer c
             Direction = direction;
             Comparer = comparer;
         }
+
+        private class ObjectComparer : IComparer
+        {
+            public static readonly IComparer Instance = new ObjectComparer();
+
+            private ObjectComparer()
+            {
+            }
+
+            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);
+            }
+        }
     }
 }