mcs/class/referencesource/mscorlib/system/collections/dictionarybase.cs

   1 // ==++==
   2 //
   3 //   Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 // ==--==
   6 //------------------------------------------------------------------------------
   7 //------------------------------------------------------------------------------
   8 // <OWNER>[....]</OWNER>
   9 //
  10
  11 namespace System.Collections {
  12
  13     using System;
  14     using System.Security.Permissions;
  15
  16     // Useful base class for typed read/write collections where items derive from object
  17     [Serializable]
  18 [System.Runtime.InteropServices.ComVisible(true)]
  19     public abstract class DictionaryBase : IDictionary {
  20         Hashtable hashtable;
  21
  22         protected Hashtable InnerHashtable {
  23             get {
  24                 if (hashtable == null)
  25                     hashtable = new Hashtable();
  26                 return hashtable;
  27             }
  28         }
  29
  30         protected IDictionary Dictionary {
  31             get { return (IDictionary) this; }
  32         }
  33
  34         public int Count {
  35             // to avoid newing inner list if no items are ever added
  36             get { return hashtable == null ? 0 : hashtable.Count; }
  37         }
  38
  39         bool IDictionary.IsReadOnly {
  40             get { return InnerHashtable.IsReadOnly; }
  41         }
  42
  43         bool IDictionary.IsFixedSize {
  44             get { return InnerHashtable.IsFixedSize; }
  45         }
  46
  47         bool ICollection.IsSynchronized {
  48             get { return InnerHashtable.IsSynchronized; }
  49         }
  50
  51         ICollection IDictionary.Keys {
  52             get {
  53                 return InnerHashtable.Keys;
  54             }
  55         }
  56
  57         Object ICollection.SyncRoot {
  58             get { return InnerHashtable.SyncRoot; }
  59         }
  60
  61         ICollection IDictionary.Values {
  62             get {
  63                 return InnerHashtable.Values;
  64             }
  65         }
  66
  67         public void CopyTo(Array array, int index) {
  68             InnerHashtable.CopyTo(array, index);
  69         }
  70
  71         object IDictionary.this[object key] {
  72             get {
  73                 object currentValue = InnerHashtable[key];
  74                 OnGet(key, currentValue);
  75                 return currentValue;
  76             }
  77             set {
  78                 OnValidate(key, value);
  79                 bool keyExists = true;
  80                 Object temp = InnerHashtable[key];
  81                 if( temp == null) {
  82                     keyExists = InnerHashtable.Contains(key);
  83                 }
  84
  85                 OnSet(key, temp, value);
  86                 InnerHashtable[key] = value;
  87                 try {
  88                     OnSetComplete(key, temp, value);
  89                 }
  90                 catch {
  91                    if( keyExists) {
  92                        InnerHashtable[key] = temp;
  93                    }
  94                    else {
  95                        InnerHashtable.Remove(key);
  96                    }
  97                    throw;
  98                 }
  99             }
 100         }
 101
 102         bool IDictionary.Contains(object key) {
 103             return InnerHashtable.Contains(key);
 104         }
 105
 106         void IDictionary.Add(object key, object value) {
 107             OnValidate(key, value);
 108             OnInsert(key, value);
 109             InnerHashtable.Add(key, value);
 110             try {
 111                 OnInsertComplete(key, value);
 112             }
 113             catch {
 114                 InnerHashtable.Remove(key);
 115                 throw;
 116             }
 117         }
 118
 119         public void Clear() {
 120             OnClear();
 121             InnerHashtable.Clear();
 122             OnClearComplete();
 123         }
 124
 125         void IDictionary.Remove(object key) {
 126             if(InnerHashtable.Contains(key)) {
 127                 Object temp = InnerHashtable[key];
 128                 OnValidate(key, temp);
 129                 OnRemove(key, temp);
 130
 131                 InnerHashtable.Remove(key);
 132                 try {
 133                     OnRemoveComplete(key, temp);
 134                 }
 135                 catch {
 136                     InnerHashtable.Add(key, temp);
 137                     throw;
 138                 }
 139             }
 140         }
 141
 142         public IDictionaryEnumerator GetEnumerator() {
 143             return InnerHashtable.GetEnumerator();
 144         }
 145
 146         IEnumerator IEnumerable.GetEnumerator() {
 147             return InnerHashtable.GetEnumerator();
 148         }
 149
 150         protected virtual object OnGet(object key, object currentValue) {
 151             return currentValue;
 152         }
 153
 154         protected virtual void OnSet(object key, object oldValue, object newValue) {
 155         }
 156
 157         protected virtual void OnInsert(object key, object value) {
 158         }
 159
 160         protected virtual void OnClear() {
 161         }
 162
 163         protected virtual void OnRemove(object key, object value) {
 164         }
 165
 166         protected virtual void OnValidate(object key, object value) {
 167         }
 168
 169         protected virtual void OnSetComplete(object key, object oldValue, object newValue) {
 170         }
 171
 172         protected virtual void OnInsertComplete(object key, object value) {
 173         }
 174
 175         protected virtual void OnClearComplete() {
 176         }
 177
 178         protected virtual void OnRemoveComplete(object key, object value) {
 179         }
 180
 181     }
 182
 183 }