IDictionary インターフェイス
キー/値ペアの非ジェネリック コレクションを表します。 名前空間: System.Collections
アセンブリ: mscorlib (mscorlib.dll 内)
構文
解説
使用例
プラットフォーム
バージョン情報
参照
アセンブリ: mscorlib (mscorlib.dll 内)
構文解説IDictionary インターフェイスは、キー/値ペアの非ジェネリック コレクションに対する基本インターフェイスです。このインターフェイスのジェネリック バージョンについては、「System.Collections.Generic.IDictionary」を参照してください。
各要素は、DictionaryEntry オブジェクトに格納されているキー/値ペアです。
各ペアが一意なキーを持っている必要があります。キーを null 参照 (Visual Basic では Nothing) にできるかどうかは、実装によって異なります。キーの値が null 参照 (Visual Basic では Nothing) になることを許容する場合は、キーを一意にする必要はありません。IDictionary インターフェイスを使用すると、保持されているキーと値を列挙できますが、特定の並べ替え順序は指定できません。
IDictionary の実装には、読み取り専用、固定サイズ、および可変サイズの 3 種類があります。読み取り専用の IDictionary オブジェクトは、変更できません。固定サイズの IDictionary オブジェクトでは、要素の追加または削除はできませんが、既存の要素は変更できます。可変サイズの IDictionary オブジェクトでは、要素を追加、削除、および変更できます。
C# 言語の foreach ステートメント (Visual Basic では for each) は、コレクション内の各要素の型を必要とします。IDictionary オブジェクトの各要素はキー/値ペアであるため、要素の型は、キーの型や値の型にはなりません。その代わり、要素の型は DictionaryEntry になります。次に例を示します。
foreach (DictionaryEntry de in myHashtable) {...}
For Each de As DictionaryEntry In myHashtable ... Next myDE
foreach ステートメントは、列挙子のラッパーです。これは、コレクションからの読み取りだけを許可し、コレクションへの書き込みを防ぎます。
実装時の注意 実装クラスは、キーを比較する手段を備えている必要があります。使用例IDictionary インターフェイスを実装する単純なディクショナリ クラスを定義する方法を次のコード例に示します。
' This class implements a simple dictionary using an array of DictionaryEntry objects (key/value pairs). Public Class SimpleDictionary Implements IDictionary ' The array of items Dim items() As DictionaryEntry Dim ItemsInUse As Integer = 0 ' Construct the SimpleDictionary with the desired number of items. ' The number of items cannot change for the life time of this SimpleDictionary. Public Sub New(ByVal numItems As Integer) items = New DictionaryEntry(numItems - 1) {} End Sub ' IDictionary Members Public ReadOnly Property IsReadOnly() As Boolean Implements IDictionary.IsReadOnly Get Return False End Get End Property Public Function Contains(ByVal key As Object) As Boolean Implements IDictionary.Contains Dim index As Integer Return TryGetIndexOfKey(key, index) End Function Public ReadOnly Property IsFixedSize() As Boolean Implements IDictionary.IsFixedSize Get Return False End Get End Property Public Sub Remove(ByVal key As Object) Implements IDictionary.Remove If key = Nothing Then Throw New ArgumentNullException("key") End If ' Try to find the key in the DictionaryEntry array Dim index As Integer If TryGetIndexOfKey(key, index) Then ' If the key is found, slide all the items up. Array.Copy(items, index + 1, items, index, (ItemsInUse - index) - 1) ItemsInUse = ItemsInUse - 1 Else ' If the key is not in the dictionary, just return. End If End Sub Public Sub Clear() Implements IDictionary.Clear ItemsInUse = 0 End Sub Public Sub Add(ByVal key As Object, ByVal value As Object) Implements IDictionary.Add ' Add the new key/value pair even if this key already exists in the dictionary. If ItemsInUse = items.Length Then Throw New InvalidOperationException("The dictionary cannot hold any more items.") End If items(ItemsInUse) = New DictionaryEntry(key, value) ItemsInUse = ItemsInUse + 1 End Sub Public ReadOnly Property Keys() As ICollection Implements IDictionary.Keys Get ' Return an array where each item is a key. Dim keyArray() As Object = New Object(ItemsInUse - 1) {} Dim n As Integer For n = 0 To ItemsInUse - 1 keyArray(n) = items(n).Key Next n Return keyArray End Get End Property Public ReadOnly Property Values() As ICollection Implements IDictionary.Values Get ' Return an array where each item is a value. Dim valueArray() As Object = New Object(ItemsInUse - 1) {} Dim n As Integer For n = 0 To ItemsInUse - 1 valueArray(n) = items(n).Value Next n Return valueArray End Get End Property Public Property Item(ByVal key As Object) As Object Implements IDictionary.Item Get ' If this key is in the dictionary, return its value. Dim index As Integer If TryGetIndexOfKey(key, index) Then ' The key was found return its value. Return items(index).Value Else ' The key was not found return null. Return Nothing End If End Get Set(ByVal value As Object) ' If this key is in the dictionary, change its value. Dim index As Integer If TryGetIndexOfKey(key, index) Then ' The key was found change its value. items(index).Value = value Else ' This key is not in the dictionary add this key/value pair. Add(key, value) End If End Set End Property Private Function TryGetIndexOfKey(ByVal key As Object, ByRef index As Integer) As Boolean For index = 0 To ItemsInUse - 1 ' If the key is found, return true (the index is also returned). If items(index).Key.Equals(key) Then Return True End If Next index ' Key not found, return false (index should be ignored by the caller). Return False End Function
// This class implements a simple dictionary using an array of DictionaryEntry objects (key/value pairs). public class SimpleDictionary : IDictionary { // The array of items private DictionaryEntry[] items; private Int32 ItemsInUse = 0; // Construct the SimpleDictionary with the desired number of items. // The number of items cannot change for the life time of this SimpleDictionary. public SimpleDictionary(Int32 numItems) { items = new DictionaryEntry[numItems]; } #region IDictionary Members public bool IsReadOnly { get { return false; } } public bool Contains(object key) { Int32 index; return TryGetIndexOfKey(key, out index); } public bool IsFixedSize { get { return false; } } public void Remove(object key) { if (key == null) throw new ArgumentNullException("key"); // Try to find the key in the DictionaryEntry array Int32 index; if (TryGetIndexOfKey(key, out index)) { // If the key is found, slide all the items up. Array.Copy(items, index + 1, items, index, ItemsInUse - index - 1); ItemsInUse--; } else { // If the key is not in the dictionary, just return. } } public void Clear() { ItemsInUse = 0; } public void Add(object key, object value) { // Add the new key/value pair even if this key already exists in the dictionary. if (ItemsInUse == items.Length) throw new InvalidOperationException("The dictionary cannot hold any more items."); items[ItemsInUse++] = new DictionaryEntry(key, value); } public ICollection Keys { get { // Return an array where each item is a key. Object[] keys = new Object[ItemsInUse]; for (Int32 n = 0; n < ItemsInUse; n++) keys[n] = items[n].Key; return keys; } } public ICollection Values { get { // Return an array where each item is a value. Object[] values = new Object[ItemsInUse]; for (Int32 n = 0; n < ItemsInUse; n++) values[n] = items[n].Value; return values; } } public object this[object key] { get { // If this key is in the dictionary, return its value. Int32 index; if (TryGetIndexOfKey(key, out index)) { // The key was found; return its value. return items[index].Value; } else { // The key was not found; return null. return null; } } set { // If this key is in the dictionary, change its value. Int32 index; if (TryGetIndexOfKey(key, out index)) { // The key was found; change its value. items[index].Value = value; } else { // This key is not in the dictionary; add this key/value pair. Add(key, value); } } } private Boolean TryGetIndexOfKey(Object key, out Int32 index) { for (index = 0; index < ItemsInUse; index++) { // If the key is found, return true (the index is also returned). if (items[index].Key.Equals(key)) return true; } // Key not found, return false (index should be ignored by the caller). return false; } private class SimpleDictionaryEnumerator : IDictionaryEnumerator { // A copy of the SimpleDictionary object's key/value pairs. DictionaryEntry[] items; Int32 index = -1; public SimpleDictionaryEnumerator(SimpleDictionary sd) { // Make a copy of the dictionary entries currently in the SimpleDictionary object. items = new DictionaryEntry[sd.Count]; Array.Copy(sd.items, 0, items, 0, sd.Count); } // Return the current item. public Object Current { get { ValidateIndex(); return items[index]; } } // Return the current dictionary entry. public DictionaryEntry Entry { get { return (DictionaryEntry) Current; } } // Return the key of the current item. public Object Key { get { ValidateIndex(); return items[index].Key; } } // Return the value of the current item. public Object Value { get { ValidateIndex(); return items[index].Value; } } // Advance to the next item. public Boolean MoveNext() { if (index < items.Length - 1) { index++; return true; } return false; } // Validate the enumeration index and throw an exception if the index is out of range. private void ValidateIndex() { if (index < 0 || index >= items.Length) throw new InvalidOperationException("Enumerator is before or after the collection."); } // Reset the index to restart the enumeration. public void Reset() { index = -1; } } public IDictionaryEnumerator GetEnumerator() { // Construct and return an enumerator. return new SimpleDictionaryEnumerator(this); } #endregion #region ICollection Members public bool IsSynchronized { get { return false; } } public object SyncRoot { get { throw new NotImplementedException(); } } public int Count { get { return ItemsInUse; } } public void CopyTo(Array array, int index) { throw new NotImplementedException(); } #endregion #region IEnumerable Members IEnumerator IEnumerable.GetEnumerator() { // Construct and return an enumerator. return ((IDictionary)this).GetEnumerator(); } #endregion }
// This class implements a simple dictionary using an array of // DictionaryEntry objects (key/value pairs). public ref class SimpleDictionary : public IDictionary { // The array of items private: array<DictionaryEntry^>^ items; private: int itemsInUse; // Construct the SimpleDictionary with the desired number of // items. The number of items cannot change for the life time of // this SimpleDictionary. public: SimpleDictionary(int size) { items = gcnew array<DictionaryEntry^>(size); } #pragma region IDictionary Members public: property virtual bool IsReadOnly { bool get() { return false; } } public: virtual bool Contains(Object^ key) { int index; return TryGetIndexOfKey(key, &index); } public: virtual property bool IsFixedSize { bool get() { return false; } } public: virtual void Remove(Object^ key) { if (key == nullptr) { throw gcnew ArgumentNullException("key"); } // Try to find the key in the DictionaryEntry array int index; if (TryGetIndexOfKey(key, &index)) { // If the key is found, slide all the items down. Array::Copy(items, index + 1, items, index, itemsInUse - index - 1); itemsInUse--; } else { // If the key is not in the dictionary, just return. return; } } public: virtual void Clear() { itemsInUse = 0; } public: virtual void Add(Object^ key, Object^ value) { // Add the new key/value pair even if this key already exists // in the dictionary. if (itemsInUse == items->Length) { throw gcnew InvalidOperationException ("The dictionary cannot hold any more items."); } items[itemsInUse++] = gcnew DictionaryEntry(key, value); } public: virtual property ICollection^ Keys { ICollection^ get() { // Return an array where each item is a key. array<Object^>^ keys = gcnew array<Object^>(itemsInUse); for (int i = 0; i < itemsInUse; i++) { keys[i] = items[i]->Key; } return keys; } } public: virtual property ICollection^ Values { ICollection^ get() { // Return an array where each item is a value. array<Object^>^ values = gcnew array<Object^>(itemsInUse); for (int i = 0; i < itemsInUse; i++) { values[i] = items[i]->Value; } return values; } } public: virtual property Object^ default[Object^] { Object^ get(Object^ key) { // If this key is in the dictionary, return its value. int index; if (TryGetIndexOfKey(key, &index)) { // The key was found; return its value. return items[index]->Value; } else { // The key was not found; return null. return nullptr; } } void set(Object^ key, Object^ value) { // If this key is in the dictionary, change its value. int index; if (TryGetIndexOfKey(key, &index)) { // The key was found; change its value. items[index]->Value = value; } else { // This key is not in the dictionary; add this // key/value pair. Add(key, value); } } } private: bool TryGetIndexOfKey(Object^ key, int* index) { for (*index = 0; *index < itemsInUse; *index++) { // If the key is found, return true (the index is also // returned). if (items[*index]->Key->Equals(key)) { return true; } } // Key not found, return false (index should be ignored by // the caller). return false; }
プラットフォームWindows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。
バージョン情報参照- IDictionary インターフェイスのページへのリンク
