mcs/class/referencesource/System.Activities.Presentation/System.Activities.Presentation/System/Activities/Presentation/Base/Core/Internal/PropertyEditing/Model/PropertyEntryPropertyOrderComparer.cs

   1 //----------------------------------------------------------------
   2 // Copyright (c) Microsoft Corporation.  All rights reserved.
   3 //----------------------------------------------------------------
   4 namespace System.Activities.Presentation.Internal.PropertyEditing.Model
   5 {
   6     using System;
   7     using System.Collections;
   8     using System.Collections.Generic;
   9     using System.Activities.Presentation.PropertyEditing;
  10
  11     // <summary>
  12     // Compares PropertyEntry instances based on their PropertyOrder tokens
  13     // as well as their DisplayNames
  14     // </summary>
  15     internal class PropertyEntryPropertyOrderComparer : IComparer, IComparer<PropertyEntry>
  16     {
  17
  18         private static readonly PropertyOrder DefaultOrder = PropertyOrder.Default;
  19         private static PropertyEntryPropertyOrderComparer _instance;
  20
  21         // <summary>
  22         // Gets a singleton instance of this class
  23         // </summary>
  24         public static PropertyEntryPropertyOrderComparer Instance
  25         {
  26             get {
  27                 if (_instance == null)
  28                 {
  29                     _instance = new PropertyEntryPropertyOrderComparer();
  30                 }
  31
  32                 return _instance;
  33             }
  34         }
  35
  36         // <summary>
  37         // Compares two instances of PropertyEntry class, using both
  38         // PropertyOrder and DisplayName to cast its vote.
  39         // </summary>
  40         // <param name="x">Left side</param>
  41         // <param name="y">Right side</param>
  42         // <returns>Comparison result</returns>
  43         public int Compare(object x, object y)
  44         {
  45             return CompareCore(x, y);
  46         }
  47
  48         // <summary>
  49         // Compares two instances of PropertyEntry class, using both
  50         // PropertyOrder and DisplayName to cast its vote.
  51         // Same method, different signature.
  52         // </summary>
  53         // <param name="x">Left</param>
  54         // <param name="y">Right</param>
  55         // <param name="x">Left side</param>
  56         // <param name="y">Right side</param>
  57         // <returns>Comparison result</returns>
  58         public int Compare(PropertyEntry x, PropertyEntry y)
  59         {
  60             return CompareCore(x, y);
  61         }
  62
  63         private static int CompareCore(object x, object y)
  64         {
  65             ModelPropertyEntry j = x as ModelPropertyEntry;
  66             ModelPropertyEntry k = y as ModelPropertyEntry;
  67
  68             if (j == null && k == null)
  69             {
  70                 return 0;
  71             }
  72             if (j == null)
  73             {
  74                 return -1;
  75             }
  76             if (k == null)
  77             {
  78                 return 1;
  79             }
  80
  81             PropertyOrder a = j.PropertyOrder ?? DefaultOrder;
  82             PropertyOrder b = k.PropertyOrder ?? DefaultOrder;
  83
  84             int result = a.CompareTo(b);
  85
  86             return result != 0 ? result : string.Compare(j.DisplayName, k.DisplayName, StringComparison.CurrentCulture);
  87         }
  88     }
  89 }