DictionaryBase.GetEnumerator Метод
Определение
Важно!
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Возвращает перечислитель IDictionaryEnumerator, осуществляющий перебор элементов экземпляра класса DictionaryBase.
public:
virtual System::Collections::IDictionaryEnumerator ^ GetEnumerator();public System.Collections.IDictionaryEnumerator GetEnumerator ();abstract member GetEnumerator : unit -> System.Collections.IDictionaryEnumerator
override this.GetEnumerator : unit -> System.Collections.IDictionaryEnumeratorPublic Function GetEnumerator () As IDictionaryEnumeratorВозвращаемое значение
Перечислитель IDictionaryEnumerator для экземпляра класса DictionaryBase.
Реализации
Примеры
В следующем примере кода реализуется DictionaryBase класс и используется эта реализация для создания словаря ключей String и значений Length , которые содержат не более пяти символов.
using namespace System;
using namespace System::Collections;
public ref class ShortStringDictionary: public DictionaryBase
{
public:
property String^ Item [String^]
{
String^ get( String^ key )
{
return (dynamic_cast<String^>(Dictionary[ key ]));
}
void set( String^ value, String^ key )
{
Dictionary[ key ] = value;
}
}
property ICollection^ Keys
{
ICollection^ get()
{
return (Dictionary->Keys);
}
}
property ICollection^ Values
{
ICollection^ get()
{
return (Dictionary->Values);
}
}
void Add( String^ key, String^ value )
{
Dictionary->Add( key, value );
}
bool Contains( String^ key )
{
return (Dictionary->Contains( key ));
}
void Remove( String^ key )
{
Dictionary->Remove( key );
}
protected:
virtual void OnInsert( Object^ key, Object^ value ) override
{
if ( key->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "key must be of type String.","key" );
else
{
String^ strKey = dynamic_cast<String^>(key);
if ( strKey->Length > 5 )
throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
}
if ( value->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "value must be of type String.","value" );
else
{
String^ strValue = dynamic_cast<String^>(value);
if ( strValue->Length > 5 )
throw gcnew ArgumentException( "value must be no more than 5 characters in length.","value" );
}
}
virtual void OnRemove( Object^ key, Object^ /*value*/ ) override
{
if ( key->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "key must be of type String.","key" );
else
{
String^ strKey = dynamic_cast<String^>(key);
if ( strKey->Length > 5 )
throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
}
}
virtual void OnSet( Object^ key, Object^ /*oldValue*/, Object^ newValue ) override
{
if ( key->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "key must be of type String.","key" );
else
{
String^ strKey = dynamic_cast<String^>(key);
if ( strKey->Length > 5 )
throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
}
if ( newValue->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "newValue must be of type String.","newValue" );
else
{
String^ strValue = dynamic_cast<String^>(newValue);
if ( strValue->Length > 5 )
throw gcnew ArgumentException( "newValue must be no more than 5 characters in length.","newValue" );
}
}
virtual void OnValidate( Object^ key, Object^ value ) override
{
if ( key->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "key must be of type String.","key" );
else
{
String^ strKey = dynamic_cast<String^>(key);
if ( strKey->Length > 5 )
throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
}
if ( value->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "value must be of type String.","value" );
else
{
String^ strValue = dynamic_cast<String^>(value);
if ( strValue->Length > 5 )
throw gcnew ArgumentException( "value must be no more than 5 characters in length.","value" );
}
}
};
void PrintKeysAndValues2( ShortStringDictionary^ myCol );
void PrintKeysAndValues3( ShortStringDictionary^ myCol );
int main()
{
// Creates and initializes a new DictionaryBase.
ShortStringDictionary^ mySSC = gcnew ShortStringDictionary;
// Adds elements to the collection.
mySSC->Add( "One", "a" );
mySSC->Add( "Two", "ab" );
mySSC->Add( "Three", "abc" );
mySSC->Add( "Four", "abcd" );
mySSC->Add( "Five", "abcde" );
// Display the contents of the collection using the enumerator.
Console::WriteLine( "Contents of the collection (using enumerator):" );
PrintKeysAndValues2( mySSC );
// Display the contents of the collection using the Keys property and the Item property.
Console::WriteLine( "Initial contents of the collection (using Keys and Item):" );
PrintKeysAndValues3( mySSC );
// Tries to add a value that is too long.
try
{
mySSC->Add( "Ten", "abcdefghij" );
}
catch ( ArgumentException^ e )
{
Console::WriteLine( e );
}
// Tries to add a key that is too long.
try
{
mySSC->Add( "Eleven", "ijk" );
}
catch ( ArgumentException^ e )
{
Console::WriteLine( e );
}
Console::WriteLine();
// Searches the collection with Contains.
Console::WriteLine( "Contains \"Three\": {0}", mySSC->Contains( "Three" ) );
Console::WriteLine( "Contains \"Twelve\": {0}", mySSC->Contains( "Twelve" ) );
Console::WriteLine();
// Removes an element from the collection.
mySSC->Remove( "Two" );
// Displays the contents of the collection.
Console::WriteLine( "After removing \"Two\":" );
PrintKeysAndValues2( mySSC );
}
// Uses the enumerator.
void PrintKeysAndValues2( ShortStringDictionary^ myCol )
{
DictionaryEntry myDE;
System::Collections::IEnumerator^ myEnumerator = myCol->GetEnumerator();
while ( myEnumerator->MoveNext() )
if ( myEnumerator->Current != nullptr )
{
myDE = *dynamic_cast<DictionaryEntry^>(myEnumerator->Current);
Console::WriteLine( " {0,-5} : {1}", myDE.Key, myDE.Value );
}
Console::WriteLine();
}
// Uses the Keys property and the Item property.
void PrintKeysAndValues3( ShortStringDictionary^ myCol )
{
ICollection^ myKeys = myCol->Keys;
IEnumerator^ myEnum1 = myKeys->GetEnumerator();
while ( myEnum1->MoveNext() )
{
String^ k = safe_cast<String^>(myEnum1->Current);
Console::WriteLine( " {0,-5} : {1}", k, myCol->Item[ k ] );
}
Console::WriteLine();
}
/*
This code produces the following output.
Contents of the collection (using enumerator):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
Initial contents of the collection (using Keys and Item):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
System.ArgumentException: value must be no more than 5 characters in length.
Parameter name: value
at ShortStringDictionary.OnValidate(Object key, Object value)
at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
at SamplesDictionaryBase.Main()
System.ArgumentException: key must be no more than 5 characters in length.
Parameter name: key
at ShortStringDictionary.OnValidate(Object key, Object value)
at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
at SamplesDictionaryBase.Main()
Contains "Three": True
Contains "Twelve": False
After removing "Two":
Three : abc
Five : abcde
One : a
Four : abcd
*/
using System;
using System.Collections;
public class ShortStringDictionary : DictionaryBase {
public String this[ String key ] {
get {
return( (String) Dictionary[key] );
}
set {
Dictionary[key] = value;
}
}
public ICollection Keys {
get {
return( Dictionary.Keys );
}
}
public ICollection Values {
get {
return( Dictionary.Values );
}
}
public void Add( String key, String value ) {
Dictionary.Add( key, value );
}
public bool Contains( String key ) {
return( Dictionary.Contains( key ) );
}
public void Remove( String key ) {
Dictionary.Remove( key );
}
protected override void OnInsert( Object key, Object value ) {
if ( key.GetType() != typeof(System.String) )
{
throw new ArgumentException( "key must be of type String.", "key" );
}
else {
String strKey = (String) key;
if ( strKey.Length > 5 )
throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
}
if ( value.GetType() != typeof(System.String) )
{
throw new ArgumentException( "value must be of type String.", "value" );
}
else {
String strValue = (String) value;
if ( strValue.Length > 5 )
throw new ArgumentException( "value must be no more than 5 characters in length.", "value" );
}
}
protected override void OnRemove( Object key, Object value ) {
if ( key.GetType() != typeof(System.String) )
{
throw new ArgumentException( "key must be of type String.", "key" );
}
else {
String strKey = (String) key;
if ( strKey.Length > 5 )
throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
}
}
protected override void OnSet( Object key, Object oldValue, Object newValue ) {
if ( key.GetType() != typeof(System.String) )
{
throw new ArgumentException( "key must be of type String.", "key" );
}
else {
String strKey = (String) key;
if ( strKey.Length > 5 )
throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
}
if ( newValue.GetType() != typeof(System.String) )
{
throw new ArgumentException( "newValue must be of type String.", "newValue" );
}
else {
String strValue = (String) newValue;
if ( strValue.Length > 5 )
throw new ArgumentException( "newValue must be no more than 5 characters in length.", "newValue" );
}
}
protected override void OnValidate( Object key, Object value ) {
if ( key.GetType() != typeof(System.String) )
{
throw new ArgumentException( "key must be of type String.", "key" );
}
else {
String strKey = (String) key;
if ( strKey.Length > 5 )
throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
}
if ( value.GetType() != typeof(System.String) )
{
throw new ArgumentException( "value must be of type String.", "value" );
}
else {
String strValue = (String) value;
if ( strValue.Length > 5 )
throw new ArgumentException( "value must be no more than 5 characters in length.", "value" );
}
}
}
public class SamplesDictionaryBase {
public static void Main() {
// Creates and initializes a new DictionaryBase.
ShortStringDictionary mySSC = new ShortStringDictionary();
// Adds elements to the collection.
mySSC.Add( "One", "a" );
mySSC.Add( "Two", "ab" );
mySSC.Add( "Three", "abc" );
mySSC.Add( "Four", "abcd" );
mySSC.Add( "Five", "abcde" );
// Display the contents of the collection using foreach. This is the preferred method.
Console.WriteLine( "Contents of the collection (using foreach):" );
PrintKeysAndValues1( mySSC );
// Display the contents of the collection using the enumerator.
Console.WriteLine( "Contents of the collection (using enumerator):" );
PrintKeysAndValues2( mySSC );
// Display the contents of the collection using the Keys property and the Item property.
Console.WriteLine( "Initial contents of the collection (using Keys and Item):" );
PrintKeysAndValues3( mySSC );
// Tries to add a value that is too long.
try {
mySSC.Add( "Ten", "abcdefghij" );
}
catch ( ArgumentException e ) {
Console.WriteLine( e.ToString() );
}
// Tries to add a key that is too long.
try {
mySSC.Add( "Eleven", "ijk" );
}
catch ( ArgumentException e ) {
Console.WriteLine( e.ToString() );
}
Console.WriteLine();
// Searches the collection with Contains.
Console.WriteLine( "Contains \"Three\": {0}", mySSC.Contains( "Three" ) );
Console.WriteLine( "Contains \"Twelve\": {0}", mySSC.Contains( "Twelve" ) );
Console.WriteLine();
// Removes an element from the collection.
mySSC.Remove( "Two" );
// Displays the contents of the collection.
Console.WriteLine( "After removing \"Two\":" );
PrintKeysAndValues1( mySSC );
}
// Uses the foreach statement which hides the complexity of the enumerator.
// NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
public static void PrintKeysAndValues1( ShortStringDictionary myCol ) {
foreach ( DictionaryEntry myDE in myCol )
Console.WriteLine( " {0,-5} : {1}", myDE.Key, myDE.Value );
Console.WriteLine();
}
// Uses the enumerator.
// NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
public static void PrintKeysAndValues2( ShortStringDictionary myCol ) {
DictionaryEntry myDE;
System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
while ( myEnumerator.MoveNext() )
if ( myEnumerator.Current != null ) {
myDE = (DictionaryEntry) myEnumerator.Current;
Console.WriteLine( " {0,-5} : {1}", myDE.Key, myDE.Value );
}
Console.WriteLine();
}
// Uses the Keys property and the Item property.
public static void PrintKeysAndValues3( ShortStringDictionary myCol ) {
ICollection myKeys = myCol.Keys;
foreach ( String k in myKeys )
Console.WriteLine( " {0,-5} : {1}", k, myCol[k] );
Console.WriteLine();
}
}
/*
This code produces the following output.
Contents of the collection (using foreach):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
Contents of the collection (using enumerator):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
Initial contents of the collection (using Keys and Item):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
System.ArgumentException: value must be no more than 5 characters in length.
Parameter name: value
at ShortStringDictionary.OnValidate(Object key, Object value)
at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
at SamplesDictionaryBase.Main()
System.ArgumentException: key must be no more than 5 characters in length.
Parameter name: key
at ShortStringDictionary.OnValidate(Object key, Object value)
at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
at SamplesDictionaryBase.Main()
Contains "Three": True
Contains "Twelve": False
After removing "Two":
Three : abc
Five : abcde
One : a
Four : abcd
*/
Imports System.Collections
Public Class ShortStringDictionary
Inherits DictionaryBase
Default Public Property Item(key As String) As String
Get
Return CType(Dictionary(key), String)
End Get
Set
Dictionary(key) = value
End Set
End Property
Public ReadOnly Property Keys() As ICollection
Get
Return Dictionary.Keys
End Get
End Property
Public ReadOnly Property Values() As ICollection
Get
Return Dictionary.Values
End Get
End Property
Public Sub Add(key As String, value As String)
Dictionary.Add(key, value)
End Sub
Public Function Contains(key As String) As Boolean
Return Dictionary.Contains(key)
End Function 'Contains
Public Sub Remove(key As String)
Dictionary.Remove(key)
End Sub
Protected Overrides Sub OnInsert(key As Object, value As Object)
If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As String = CType(key, String)
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
If Not GetType(System.String).IsAssignableFrom(value.GetType()) Then
Throw New ArgumentException("value must be of type String.", "value")
Else
Dim strValue As String = CType(value, String)
If strValue.Length > 5 Then
Throw New ArgumentException("value must be no more than 5 characters in length.", "value")
End If
End If
End Sub
Protected Overrides Sub OnRemove(key As Object, value As Object)
If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As String = CType(key, String)
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
End Sub
Protected Overrides Sub OnSet(key As Object, oldValue As Object, newValue As Object)
If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As String = CType(key, String)
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
If Not GetType(System.String).IsAssignableFrom(newValue.GetType()) Then
Throw New ArgumentException("newValue must be of type String.", "newValue")
Else
Dim strValue As String = CType(newValue, String)
If strValue.Length > 5 Then
Throw New ArgumentException("newValue must be no more than 5 characters in length.", "newValue")
End If
End If
End Sub
Protected Overrides Sub OnValidate(key As Object, value As Object)
If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As String = CType(key, String)
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
If Not GetType(System.String).IsAssignableFrom(value.GetType()) Then
Throw New ArgumentException("value must be of type String.", "value")
Else
Dim strValue As String = CType(value, String)
If strValue.Length > 5 Then
Throw New ArgumentException("value must be no more than 5 characters in length.", "value")
End If
End If
End Sub
End Class
Public Class SamplesDictionaryBase
Public Shared Sub Main()
' Creates and initializes a new DictionaryBase.
Dim mySSC As New ShortStringDictionary()
' Adds elements to the collection.
mySSC.Add("One", "a")
mySSC.Add("Two", "ab")
mySSC.Add("Three", "abc")
mySSC.Add("Four", "abcd")
mySSC.Add("Five", "abcde")
' Display the contents of the collection using For Each. This is the preferred method.
Console.WriteLine("Contents of the collection (using For Each):")
PrintKeysAndValues1(mySSC)
' Display the contents of the collection using the enumerator.
Console.WriteLine("Contents of the collection (using enumerator):")
PrintKeysAndValues2(mySSC)
' Display the contents of the collection using the Keys property and the Item property.
Console.WriteLine("Initial contents of the collection (using Keys and Item):")
PrintKeysAndValues3(mySSC)
' Tries to add a value that is too long.
Try
mySSC.Add("Ten", "abcdefghij")
Catch e As ArgumentException
Console.WriteLine(e.ToString())
End Try
' Tries to add a key that is too long.
Try
mySSC.Add("Eleven", "ijk")
Catch e As ArgumentException
Console.WriteLine(e.ToString())
End Try
Console.WriteLine()
' Searches the collection with Contains.
Console.WriteLine("Contains ""Three"": {0}", mySSC.Contains("Three"))
Console.WriteLine("Contains ""Twelve"": {0}", mySSC.Contains("Twelve"))
Console.WriteLine()
' Removes an element from the collection.
mySSC.Remove("Two")
' Displays the contents of the collection.
Console.WriteLine("After removing ""Two"":")
PrintKeysAndValues1(mySSC)
End Sub
' Uses the For Each statement which hides the complexity of the enumerator.
' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
Public Shared Sub PrintKeysAndValues1(myCol As ShortStringDictionary)
Dim myDE As DictionaryEntry
For Each myDE In myCol
Console.WriteLine(" {0,-5} : {1}", myDE.Key, myDE.Value)
Next myDE
Console.WriteLine()
End Sub
' Uses the enumerator.
' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
Public Shared Sub PrintKeysAndValues2(myCol As ShortStringDictionary)
Dim myDE As DictionaryEntry
Dim myEnumerator As System.Collections.IEnumerator = myCol.GetEnumerator()
While myEnumerator.MoveNext()
If Not (myEnumerator.Current Is Nothing) Then
myDE = CType(myEnumerator.Current, DictionaryEntry)
Console.WriteLine(" {0,-5} : {1}", myDE.Key, myDE.Value)
End If
End While
Console.WriteLine()
End Sub
' Uses the Keys property and the Item property.
Public Shared Sub PrintKeysAndValues3(myCol As ShortStringDictionary)
Dim myKeys As ICollection = myCol.Keys
Dim k As String
For Each k In myKeys
Console.WriteLine(" {0,-5} : {1}", k, myCol(k))
Next k
Console.WriteLine()
End Sub
End Class
'This code produces the following output.
'
'Contents of the collection (using For Each):
' Three : abc
' Five : abcde
' Two : ab
' One : a
' Four : abcd
'
'Contents of the collection (using enumerator):
' Three : abc
' Five : abcde
' Two : ab
' One : a
' Four : abcd
'
'Initial contents of the collection (using Keys and Item):
' Three : abc
' Five : abcde
' Two : ab
' One : a
' Four : abcd
'
'System.ArgumentException: value must be no more than 5 characters in length.
'Parameter name: value
' at ShortStringDictionary.OnValidate(Object key, Object value)
' at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
' at SamplesDictionaryBase.Main()
'System.ArgumentException: key must be no more than 5 characters in length.
'Parameter name: key
' at ShortStringDictionary.OnValidate(Object key, Object value)
' at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
' at SamplesDictionaryBase.Main()
'
'Contains "Three": True
'Contains "Twelve": False
'
'After removing "Two":
' Three : abc
' Five : abcde
' One : a
' Four : abcd
Комментарии
Инструкция foreach языка C# (for each в Visual Basic) позволяет скрыть сложный механизм перечислителей. Поэтому рекомендуется вместо непосредственного использования перечислителя применять ключевое слово foreach.
Перечислители могут использоваться для чтения данных в коллекции, но не для ее изменения.
Изначально перечислитель располагается перед первым элементом коллекции. Метод Reset также переводит перечислитель в эту позицию. В этой позиции значение свойства Current не определено. Поэтому необходимо вызвать метод MoveNext, чтобы переместить перечислитель к первому элементу коллекции до считывания значения свойства Current.
Current возвращает тот же объект, пока не будет вызван метод MoveNext или Reset. MoveNext задает Current в качестве значения для следующего элемента.
Если MoveNext передает конец коллекции, перечислитель размещается после последнего элемента в коллекции и MoveNext возвращает значение false. Если перечислитель находится в этой позиции, последующие вызовы также MoveNext возвращают .false Если последний вызов MoveNext возвращал false, Current значение не определено. Чтобы снова задать в качестве значения свойства Current первый элемент коллекции, можно последовательно вызвать методы Reset иMoveNext.
Перечислитель является допустимым до тех пор, пока коллекция остается неизменной. Если в коллекцию вносятся изменения, например добавляются, изменяются или удаляются элементы, перечислитель становится недействительным без возможности восстановление, а его поведение не определено.
У перечислителя нет эксклюзивного доступа к коллекции, поэтому перечисление коллекции не является потокобезопасной процедурой. Чтобы гарантировать потокобезопасность, можно заблокировать коллекцию на время всего перечисления. Чтобы разрешить доступ к коллекции из нескольких потоков для чтения и записи, необходимо реализовать собственную синхронизацию.
Этот метод является операцией O(1) .
Применяется к
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