IDictionaryEnumerator 介面
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
列舉非泛型字典的專案。
public interface class IDictionaryEnumerator : System::Collections::IEnumeratorpublic interface IDictionaryEnumerator : System.Collections.IEnumerator[System.Runtime.InteropServices.ComVisible(true)]
public interface IDictionaryEnumerator : System.Collections.IEnumeratortype IDictionaryEnumerator = interface
interface IEnumerator[<System.Runtime.InteropServices.ComVisible(true)>]
type IDictionaryEnumerator = interface
interface IEnumeratorPublic Interface IDictionaryEnumerator
Implements IEnumerator- 衍生
- 屬性
- 實作
範例
此程式代碼範例示範如何定義實作 IDictionaryEnumerator 介面的字典列舉值。
using namespace System;
using namespace System::Collections;
// 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;
}
private:
ref class SimpleDictionaryEnumerator : public IDictionaryEnumerator
{
// A copy of the SimpleDictionary object's key/value pairs.
private:
array<DictionaryEntry^>^ items;
private:
int index;
public:
SimpleDictionaryEnumerator(SimpleDictionary^ sd)
{
// Make a copy of the dictionary entries currently in the
// SimpleDictionary object.
items = gcnew array<DictionaryEntry^>(sd->Count);
Array::Copy(sd->items, 0, items, 0, sd->Count);
index = -1;
}
// Return the current item.
public:
virtual property Object^ Current
{
Object^ get()
{
ValidateIndex();
return items[index];
}
}
// Return the current dictionary entry.
public:
virtual property DictionaryEntry Entry
{
DictionaryEntry get()
{
return (DictionaryEntry) Current;
}
}
// Return the key of the current item.
public:
virtual property Object^ Key
{
Object^ get()
{
ValidateIndex();
return items[index]->Key;
}
}
// Return the value of the current item.
public:
virtual property Object^ Value
{
Object^ get()
{
ValidateIndex();
return items[index]->Value;
}
}
// Advance to the next item.
public:
virtual bool 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 gcnew InvalidOperationException
("Enumerator is before or after the collection.");
}
}
// Reset the index to restart the enumeration.
public:
virtual void Reset()
{
index = -1;
}
};
public:
virtual IDictionaryEnumerator^ GetEnumerator()
{
// Construct and return an enumerator.
return gcnew SimpleDictionaryEnumerator(this);
}
#pragma endregion
#pragma region ICollection Members
public:
virtual property bool IsSynchronized
{
bool get()
{
return false;
}
}
public:
virtual property Object^ SyncRoot
{
Object^ get()
{
throw gcnew NotImplementedException();
}
}
public:
virtual property int Count
{
int get()
{
return itemsInUse;
}
}
public:
virtual void CopyTo(Array^ array, int index)
{
throw gcnew NotImplementedException();
}
#pragma endregion
#pragma region IEnumerable Members
virtual IEnumerator^ IEnumerable_GetEnumerator()
= IEnumerable::GetEnumerator
{
// Construct and return an enumerator.
return ((IDictionary^)this)->GetEnumerator();
}
#pragma endregion
};
int main()
{
// Create a dictionary that contains no more than three
// entries.
IDictionary^ d = gcnew SimpleDictionary(3);
// Add three people and their ages to the dictionary.
d->Add("Jeff", 40);
d->Add("Kristin", 34);
d->Add("Aidan", 1);
Console::WriteLine("Number of elements in dictionary = {0}",
d->Count);
Console::WriteLine("Does dictionary contain 'Jeff'? {0}",
d->Contains("Jeff"));
Console::WriteLine("Jeff's age is {0}", d["Jeff"]);
// Display every entry's key and value.
for each (DictionaryEntry^ de in d)
{
Console::WriteLine("{0} is {1} years old.", de->Key,
de->Value);
}
// Remove an entry that exists.
d->Remove("Jeff");
// Remove an entry that does not exist, but do not throw an
// exception.
d->Remove("Max");
// Show the names (keys) of the people in the dictionary.
for each (String^ s in d->Keys)
{
Console::WriteLine(s);
}
// Show the ages (values) of the people in the dictionary.
for each (int age in d->Values)
{
Console::WriteLine(age);
}
}
// This code produces the following output.
//
// Number of elements in dictionary = 3
// Does dictionary contain 'Jeff'? True
// Jeff's age is 40
// Jeff is 40 years old.
// Kristin is 34 years old.
// Aidan is 1 years old.
// Kristin
// Aidan
// 34
// 1
using System;
using System.Collections;
// 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
}
public sealed class App
{
static void Main()
{
// Create a dictionary that contains no more than three entries.
IDictionary d = new SimpleDictionary(3);
// Add three people and their ages to the dictionary.
d.Add("Jeff", 40);
d.Add("Kristin", 34);
d.Add("Aidan", 1);
Console.WriteLine("Number of elements in dictionary = {0}", d.Count);
Console.WriteLine("Does dictionary contain 'Jeff'? {0}", d.Contains("Jeff"));
Console.WriteLine("Jeff's age is {0}", d["Jeff"]);
// Display every entry's key and value.
foreach (DictionaryEntry de in d)
{
Console.WriteLine("{0} is {1} years old.", de.Key, de.Value);
}
// Remove an entry that exists.
d.Remove("Jeff");
// Remove an entry that does not exist, but do not throw an exception.
d.Remove("Max");
// Show the names (keys) of the people in the dictionary.
foreach (String s in d.Keys)
Console.WriteLine(s);
// Show the ages (values) of the people in the dictionary.
foreach (Int32 age in d.Values)
Console.WriteLine(age);
}
}
// This code produces the following output.
//
// Number of elements in dictionary = 3
// Does dictionary contain 'Jeff'? True
// Jeff's age is 40
// Jeff is 40 years old.
// Kristin is 34 years old.
// Aidan is 1 years old.
// Kristin
// Aidan
// 34
// 1
Imports System.Collections
' 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.
' Note: Declaring keyArray() to have a size of ItemsInUse - 1
' ensures that the array is properly sized, in VB.NET
' declaring an array of size N creates an array with
' 0 through N elements, including N, as opposed to N - 1
' which is the default behavior in C# and C++.
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
Private Class SimpleDictionaryEnumerator
Implements IDictionaryEnumerator
' A copy of the SimpleDictionary object's key/value pairs.
Dim items() As DictionaryEntry
Dim index As Integer = -1
Public Sub New(ByVal sd As SimpleDictionary)
' Make a copy of the dictionary entries currently in the SimpleDictionary object.
items = New DictionaryEntry(sd.Count - 1) {}
Array.Copy(sd.items, 0, items, 0, sd.Count)
End Sub
' Return the current item.
Public ReadOnly Property Current() As Object Implements IDictionaryEnumerator.Current
Get
ValidateIndex()
Return items(index)
End Get
End Property
' Return the current dictionary entry.
Public ReadOnly Property Entry() As DictionaryEntry Implements IDictionaryEnumerator.Entry
Get
Return Current
End Get
End Property
' Return the key of the current item.
Public ReadOnly Property Key() As Object Implements IDictionaryEnumerator.Key
Get
ValidateIndex()
Return items(index).Key
End Get
End Property
' Return the value of the current item.
Public ReadOnly Property Value() As Object Implements IDictionaryEnumerator.Value
Get
ValidateIndex()
Return items(index).Value
End Get
End Property
' Advance to the next item.
Public Function MoveNext() As Boolean Implements IDictionaryEnumerator.MoveNext
If index < items.Length - 1 Then
index = index + 1
Return True
End If
Return False
End Function
' Validate the enumeration index and throw an exception if the index is out of range.
Private Sub ValidateIndex()
If index < 0 Or index >= items.Length Then
Throw New InvalidOperationException("Enumerator is before or after the collection.")
End If
End Sub
' Reset the index to restart the enumeration.
Public Sub Reset() Implements IDictionaryEnumerator.Reset
index = -1
End Sub
End Class
Public Function GetEnumerator() As IDictionaryEnumerator Implements IDictionary.GetEnumerator
'Construct and return an enumerator.
Return New SimpleDictionaryEnumerator(Me)
End Function
' ICollection Members
Public ReadOnly Property IsSynchronized() As Boolean Implements IDictionary.IsSynchronized
Get
Return False
End Get
End Property
Public ReadOnly Property SyncRoot() As Object Implements IDictionary.SyncRoot
Get
Throw New NotImplementedException()
End Get
End Property
Public ReadOnly Property Count() As Integer Implements IDictionary.Count
Get
Return ItemsInUse
End Get
End Property
Public Sub CopyTo(ByVal array As Array, ByVal index As Integer) Implements IDictionary.CopyTo
Throw New NotImplementedException()
End Sub
' IEnumerable Members
Public Function GetEnumerator1() As IEnumerator Implements IEnumerable.GetEnumerator
' Construct and return an enumerator.
Return Me.GetEnumerator()
End Function
End Class
Public NotInheritable Class App
Public Shared Sub Main()
' Create a dictionary that contains no more than three entries.
Dim d As IDictionary = New SimpleDictionary(3)
' Add three people and their ages to the dictionary.
d.Add("Jeff", 40)
d.Add("Kristin", 34)
d.Add("Aidan", 1)
Console.WriteLine("Number of elements in dictionary = {0}", d.Count)
Console.WriteLine("Does dictionary contain 'Jeff'? {0}", d.Contains("Jeff"))
Console.WriteLine("Jeff's age is {0}", d("Jeff"))
' Display every entry's key and value.
Dim de As DictionaryEntry
For Each de In d
Console.WriteLine("{0} is {1} years old.", de.Key, de.Value)
Next
' Remove an entry that exists.
d.Remove("Jeff")
' Remove an entry that does not exist, but do not throw an exception.
d.Remove("Max")
' Show the names (keys) of the people in the dictionary.
Dim s As String
For Each s In d.Keys
Console.WriteLine(s)
Next
' Show the ages (values) of the people in the dictionary.
Dim age As Integer
For Each age In d.Values
Console.WriteLine(age)
Next
End Sub
End Class
' This code produces the following output.
'
' Number of elements in dictionary = 3
' Does dictionary contain 'Jeff'? True
' Jeff's age is 40
' Jeff is 40 years old.
' Kristin is 34 years old.
' Aidan is 1 years old.
' Kristin
' Aidan
' 34
' 1
備註
C# 語言的 foreach 語句（在 Visual Basic 中for each）會隱藏列舉值的複雜性。 因此，建議使用 foreach，而不是直接操作列舉值。
列舉值可用來讀取集合中的數據，但無法用來修改基礎集合。
一開始，列舉值會放在集合中的第一個專案之前。 Reset 方法也會讓列舉值回到這個位置。 在這個位置上，Current 未定義。 因此，您必須先呼叫 MoveNext 方法，將列舉值前移至集合的第一個專案，再讀取 Current的值。
Current 會傳回相同的物件，直到呼叫 MoveNext 或 Reset 為止。 MoveNext 會將 Current 設定為下一個專案。
如果 MoveNext 傳遞集合結尾，則列舉值位於集合的最後一個項目之後，MoveNext 傳回 false。 當列舉值位於這個位置時，後續呼叫 MoveNext 也會傳回 false。 如果最後一次呼叫傳回 MoveNextfalse，則 Current 未定義。 若要再次將 Current 設定為集合的第一個專案，您可以呼叫 Reset，後面接著 MoveNext。
只要集合維持不變，列舉值會維持有效狀態。 如果對集合進行變更，例如新增、修改或刪除專案，列舉值會無法復原地失效，且下一次呼叫 MoveNext 或 Reset 會擲回 InvalidOperationException。
列舉值沒有集合的獨佔存取權;因此，透過集合列舉本質上不是安全線程的程式。 即使集合同步處理，其他線程仍然可以修改集合，這會導致列舉值擲回例外狀況。 若要保證列舉期間的線程安全性，您可以在整個列舉期間鎖定集合，或攔截其他線程所做的變更所產生的例外狀況。
給實施者的注意事項
繼承自 IEnumerator 的 Current 屬性會傳回 boxed DictionaryEntryObject。 與 Entry 屬性類似，不同之處在於 Entry 會傳回 DictionaryEntry，而不是 Object。
屬性
| Current |
取得集合中位於列舉值目前位置的專案。 (繼承來源 IEnumerator) |
| Entry |
取得目前字典專案的索引鍵和值。 |
| Key |
取得目前字典專案的索引鍵。 |
| Value |
取得目前字典專案的值。 |
方法
| MoveNext() |
將列舉值前進至集合的下一個專案。 (繼承來源 IEnumerator) |
| Reset() |
將列舉值設定為其初始位置，也就是集合中第一個專案之前。 (繼承來源 IEnumerator) |
