IDictionary 接口
表示键/值对的非通用集合。
**命名空间:**System.Collections
**程序集:**mscorlib（在 mscorlib.dll 中）
语法
声明
<ComVisibleAttribute(True)> _
Public Interface IDictionary
Inherits ICollection, IEnumerable
用法
Dim instance As IDictionary
[ComVisibleAttribute(true)]
public interface IDictionary : ICollection, IEnumerable
[ComVisibleAttribute(true)]
public interface class IDictionary : ICollection, IEnumerable
/** @attribute ComVisibleAttribute(true) */
public interface IDictionary extends ICollection, IEnumerable
ComVisibleAttribute(true)
public interface IDictionary extends ICollection, IEnumerable
备注
IDictionary 接口是键/值对的非通用集合的基接口。有关该接口的泛型版本的信息，请参见 System.Collections.Generic.IDictionary。
每个元素都是一个存储在 DictionaryEntry 对象中的键/值对。
每一对都必须有唯一的键。实现在是否允许键为 空引用（在 Visual Basic 中为 Nothing） 方面有所不同。此值可以为 空引用（在 Visual Basic 中为 Nothing），并且不必是唯一的。IDictionary 接口允许对所包含的键和值进行枚举，但这并不意味着任何特定的排序顺序。
IDictionary 实现有三种类别：只读、固定大小、可变大小。无法修改只读 IDictionary 对象。固定大小的 IDictionary 对象不允许添加或移除元素，但允许修改现有元素。可变大小的 IDictionary 对象允许添加、移除和修改元素。
C# 语言中的 foreach 语句（在 Visual Basic 中为 for each）需要集合中每个元素的类型。由于 IDictionary 对象的每个元素都是一个键/值对，因此元素类型既不是键的类型，也不是值的类型。而是 DictionaryEntry 类型。例如：
foreach (DictionaryEntry de in myHashtable) {...}
For Each de As DictionaryEntry In myHashtable
...
Next myDE
foreach 语句是对枚举数的包装，它只允许从集合中读取，不允许写入集合。
给实现者的说明 实现类必须有一种方式来对键进行比较。
示例
下面的代码示例演示如何定义实现 IDictionary 接口的简单字典类。
' 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;
}
平台
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
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
.NET Compact Framework
受以下版本支持：2.0、1.0
请参见
参考
IDictionary 成员
System.Collections 命名空间
Hashtable 类
ICollection 接口