StringDictionary.GetEnumerator Metode
Definisi
Penting
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Mengembalikan enumerator yang berulang melalui kamus string.
public:
virtual System::Collections::IEnumerator ^ GetEnumerator();
public virtual System.Collections.IEnumerator GetEnumerator ();
abstract member GetEnumerator : unit -> System.Collections.IEnumerator
override this.GetEnumerator : unit -> System.Collections.IEnumerator
Public Overridable Function GetEnumerator () As IEnumerator
Mengembalikan
Yang IEnumerator berulang melalui kamus string.
Penerapan
Contoh
Contoh kode berikut menghitung elemen dari StringDictionary.
#using <System.dll>
using namespace System;
using namespace System::Collections;
using namespace System::Collections::Specialized;
void PrintKeysAndValues1( StringDictionary^ myCol );
void PrintKeysAndValues2( StringDictionary^ myCol );
void PrintKeysAndValues3( StringDictionary^ myCol );
int main()
{
// Creates and initializes a new StringDictionary.
StringDictionary^ myCol = gcnew StringDictionary;
myCol->Add( "red", "rojo" );
myCol->Add( "green", "verde" );
myCol->Add( "blue", "azul" );
// Display the contents of the collection using for each. This is the preferred method.
Console::WriteLine( "Displays the elements using for each:" );
PrintKeysAndValues1( myCol );
// Display the contents of the collection using the enumerator.
Console::WriteLine( "Displays the elements using the IEnumerator:" );
PrintKeysAndValues2( myCol );
// Display the contents of the collection using the Keys, Values, Count, and Item properties.
Console::WriteLine( "Displays the elements using the Keys, Values, Count, and Item properties:" );
PrintKeysAndValues3( myCol );
}
// 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.
void PrintKeysAndValues1( StringDictionary^ myCol ) {
Console::WriteLine( " KEY VALUE" );
for each ( DictionaryEntry^ de in myCol )
Console::WriteLine( " {0,-25} {1}", de->Key, de->Value );
Console::WriteLine();
}
// Uses the enumerator.
void PrintKeysAndValues2( StringDictionary^ myCol )
{
IEnumerator^ myEnumerator = myCol->GetEnumerator();
DictionaryEntry^ de;
Console::WriteLine( " KEY VALUE" );
while ( myEnumerator->MoveNext() )
{
de = (DictionaryEntry^)(myEnumerator->Current);
Console::WriteLine( " {0,-25} {1}", de->Key, de->Value );
}
Console::WriteLine();
}
// Uses the Keys, Values, Count, and Item properties.
void PrintKeysAndValues3( StringDictionary^ myCol )
{
array<String^>^myKeys = gcnew array<String^>(myCol->Count);
myCol->Keys->CopyTo( myKeys, 0 );
Console::WriteLine( " INDEX KEY VALUE" );
for ( int i = 0; i < myCol->Count; i++ )
Console::WriteLine( " {0,-5} {1,-25} {2}", i, myKeys[ i ], myCol[ myKeys[ i ] ] );
Console::WriteLine();
}
/*
This code produces the following output.
Displays the elements using for each:
KEY VALUE
red rojo
blue azul
green verde
Displays the elements using the IEnumerator:
KEY VALUE
red rojo
blue azul
green verde
Displays the elements using the Keys, Values, Count, and Item properties:
INDEX KEY VALUE
0 red rojo
1 blue azul
2 green verde
*/
using System;
using System.Collections;
using System.Collections.Specialized;
public class SamplesStringDictionary {
public static void Main() {
// Creates and initializes a new StringDictionary.
StringDictionary myCol = new StringDictionary();
myCol.Add( "red", "rojo" );
myCol.Add( "green", "verde" );
myCol.Add( "blue", "azul" );
// Display the contents of the collection using foreach. This is the preferred method.
Console.WriteLine( "Displays the elements using foreach:" );
PrintKeysAndValues1( myCol );
// Display the contents of the collection using the enumerator.
Console.WriteLine( "Displays the elements using the IEnumerator:" );
PrintKeysAndValues2( myCol );
// Display the contents of the collection using the Keys, Values, Count, and Item properties.
Console.WriteLine( "Displays the elements using the Keys, Values, Count, and Item properties:" );
PrintKeysAndValues3( myCol );
}
// 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( StringDictionary myCol ) {
Console.WriteLine( " KEY VALUE" );
foreach ( DictionaryEntry de in myCol )
Console.WriteLine( " {0,-25} {1}", de.Key, de.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( StringDictionary myCol ) {
IEnumerator myEnumerator = myCol.GetEnumerator();
DictionaryEntry de;
Console.WriteLine( " KEY VALUE" );
while ( myEnumerator.MoveNext() ) {
de = (DictionaryEntry) myEnumerator.Current;
Console.WriteLine( " {0,-25} {1}", de.Key, de.Value );
}
Console.WriteLine();
}
// Uses the Keys, Values, Count, and Item properties.
public static void PrintKeysAndValues3( StringDictionary myCol ) {
String[] myKeys = new String[myCol.Count];
myCol.Keys.CopyTo( myKeys, 0 );
Console.WriteLine( " INDEX KEY VALUE" );
for ( int i = 0; i < myCol.Count; i++ )
Console.WriteLine( " {0,-5} {1,-25} {2}", i, myKeys[i], myCol[myKeys[i]] );
Console.WriteLine();
}
}
/*
This code produces the following output.
Displays the elements using foreach:
KEY VALUE
red rojo
blue azul
green verde
Displays the elements using the IEnumerator:
KEY VALUE
red rojo
blue azul
green verde
Displays the elements using the Keys, Values, Count, and Item properties:
INDEX KEY VALUE
0 red rojo
1 blue azul
2 green verde
*/
Imports System.Collections
Imports System.Collections.Specialized
Public Class SamplesStringDictionary
Public Shared Sub Main()
' Creates and initializes a new StringDictionary.
Dim myCol As New StringDictionary()
myCol.Add("red", "rojo")
myCol.Add("green", "verde")
myCol.Add("blue", "azul")
' Display the contents of the collection using For Each. This is the preferred method.
Console.WriteLine("Displays the elements using For Each:")
PrintKeysAndValues1(myCol)
' Display the contents of the collection using the enumerator.
Console.WriteLine("Displays the elements using the IEnumerator:")
PrintKeysAndValues2(myCol)
' Display the contents of the collection using the Keys, Values, Count, and Item properties.
Console.WriteLine("Displays the elements using the Keys, Values, Count, and Item properties:")
PrintKeysAndValues3(myCol)
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 StringDictionary)
Console.WriteLine(" KEY VALUE")
Dim de As DictionaryEntry
For Each de In myCol
Console.WriteLine(" {0,-25} {1}", de.Key, de.Value)
Next de
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 StringDictionary)
Dim myEnumerator As IEnumerator = myCol.GetEnumerator()
Dim de As DictionaryEntry
Console.WriteLine(" KEY VALUE")
While myEnumerator.MoveNext()
de = CType(myEnumerator.Current, DictionaryEntry)
Console.WriteLine(" {0,-25} {1}", de.Key, de.Value)
End While
Console.WriteLine()
End Sub
' Uses the Keys, Values, Count, and Item properties.
Public Shared Sub PrintKeysAndValues3(myCol As StringDictionary)
Dim myKeys(myCol.Count) As String
myCol.Keys.CopyTo(myKeys, 0)
Console.WriteLine(" INDEX KEY VALUE")
Dim i As Integer
For i = 0 To myCol.Count - 1
Console.WriteLine(" {0,-5} {1,-25} {2}", i, myKeys(i), myCol(myKeys(i)))
Next i
Console.WriteLine()
End Sub
End Class
'This code produces the following output.
'
'Displays the elements using For Each:
' KEY VALUE
' red rojo
' blue azul
' green verde
'
'Displays the elements using the IEnumerator:
' KEY VALUE
' red rojo
' blue azul
' green verde
'
'Displays the elements using the Keys, Values, Count, and Item properties:
' INDEX KEY VALUE
' 0 red rojo
' 1 blue azul
' 2 green verde
Keterangan
Pernyataan foreach
bahasa C# (for each
dalam Visual Basic) menyembunyikan kompleksitas enumerator. Oleh karena itu, penggunaan foreach
disarankan, alih-alih secara langsung memanipulasi enumerator.
Enumerator dapat digunakan untuk membaca data dalam koleksi, tetapi tidak dapat digunakan untuk memodifikasi koleksi yang mendasar.
Awalnya, enumerator diposisikan sebelum elemen pertama dalam koleksi. Reset juga membawa enumerator kembali ke posisi ini. Pada posisi ini, Current tidak terdefinisi. Oleh karena itu, Anda harus memanggil MoveNext untuk memajukan enumerator ke elemen pertama koleksi sebelum membaca nilai Current.
Current mengembalikan objek yang sama hingga atau MoveNextReset dipanggil. MoveNextCurrent mengatur ke elemen berikutnya.
Jika MoveNext melewati akhir koleksi, enumerator diposisikan setelah elemen terakhir dalam koleksi dan MoveNext mengembalikan false
. Ketika enumerator berada di posisi ini, panggilan berikutnya untuk MoveNext juga mengembalikan false
. Jika panggilan terakhir untuk MoveNext dikembalikan false
, Current tidak ditentukan. Untuk mengatur Current ke elemen pertama koleksi lagi, Anda dapat memanggil Reset diikuti dengan MoveNext.
Enumerator tetap valid selama koleksi tetap tidak berubah. Jika perubahan dilakukan pada koleksi, seperti menambahkan, memodifikasi, atau menghapus elemen, enumerator tidak valid dan perilakunya tidak terdefinisi.
Enumerator tidak memiliki akses eksklusif ke koleksi; oleh karena itu, menghitung melalui koleksi secara intrinsik bukan prosedur aman utas. Untuk menjamin keamanan utas selama enumerasi, Anda dapat mengunci koleksi selama seluruh enumerasi. Untuk memungkinkan koleksi diakses oleh beberapa utas untuk membaca dan menulis, Anda harus menerapkan sinkronisasi Anda sendiri.
Metode ini adalah operasi O(1).