Array.GetEnumerator Array.GetEnumerator Array.GetEnumerator Array.GetEnumerator Method

定義

傳回 IEnumeratorArrayReturns an IEnumerator for the Array.

public:
 virtual System::Collections::IEnumerator ^ GetEnumerator();
public System.Collections.IEnumerator GetEnumerator ();
abstract member GetEnumerator : unit -> System.Collections.IEnumerator
override this.GetEnumerator : unit -> System.Collections.IEnumerator
Public Function GetEnumerator () As IEnumerator

傳回

實作

範例

下列程式碼範例示範如何使用GetEnumerator列出陣列的元素。The following code example shows how to use GetEnumerator to list the elements of an array.

using namespace System;

int main()
{
   // Creates and initializes a new Array.
   array<String^>^myArr = gcnew array<String^>(10);
   myArr[ 0 ] = "The";
   myArr[ 1 ] = "quick";
   myArr[ 2 ] = "brown";
   myArr[ 3 ] = "fox";
   myArr[ 4 ] = "jumps";
   myArr[ 5 ] = "over";
   myArr[ 6 ] = "the";
   myArr[ 7 ] = "lazy";
   myArr[ 8 ] = "dog";
   
   // Displays the values of the Array.
   int i = 0;
   System::Collections::IEnumerator^ myEnumerator = myArr->GetEnumerator();
   Console::WriteLine( "The Array contains the following values:" );
   while ( (myEnumerator->MoveNext()) && (myEnumerator->Current != nullptr) )
      Console::WriteLine( "[{0}] {1}", i++, myEnumerator->Current );
}

/* 
This code produces the following output.

The Array contains the following values:
[0] The
[1] quick
[2] brown
[3] fox
[4] jumps
[5] over
[6] the
[7] lazy
[8] dog

*/
using System;

public class SamplesArray  {
 
   public static void Main()  {
 
      // Creates and initializes a new Array.
      String[] myArr = new String[10];
      myArr[0] = "The";
      myArr[1] = "quick";
      myArr[2] = "brown";
      myArr[3] = "fox";
      myArr[4] = "jumps";
      myArr[5] = "over";
      myArr[6] = "the";
      myArr[7] = "lazy";
      myArr[8] = "dog";
 
      // Displays the values of the Array.
      int i = 0;
      System.Collections.IEnumerator myEnumerator = myArr.GetEnumerator();
      Console.WriteLine( "The Array contains the following values:" );
      while (( myEnumerator.MoveNext() ) && ( myEnumerator.Current != null ))
         Console.WriteLine( "[{0}] {1}", i++, myEnumerator.Current );

   }
 
}


/* 
This code produces the following output.

The Array contains the following values:
[0] The
[1] quick
[2] brown
[3] fox
[4] jumps
[5] over
[6] the
[7] lazy
[8] dog

*/

Imports System

Public Class SamplesArray

   Public Shared Sub Main()

      ' Creates and initializes a new Array.
      Dim myArr(10) As [String]
      myArr(0) = "The"
      myArr(1) = "quick"
      myArr(2) = "brown"
      myArr(3) = "fox"
      myArr(4) = "jumps"
      myArr(5) = "over"
      myArr(6) = "the"
      myArr(7) = "lazy"
      myArr(8) = "dog"

      ' Displays the values of the Array.
      Dim i As Integer = 0
      Dim myEnumerator As System.Collections.IEnumerator = myArr.GetEnumerator()
      Console.WriteLine("The Array contains the following values:")
      While myEnumerator.MoveNext() And Not (myEnumerator.Current Is Nothing)
         Console.WriteLine("[{0}] {1}", i, myEnumerator.Current)
         i += 1
      End While 

   End Sub 'Main

End Class 'SamplesArray 


'This code produces the following output.
'
'The Array contains the following values:
'[0] The
'[1] quick
'[2] brown
'[3] fox
'[4] jumps
'[5] over
'[6] the
'[7] lazy
'[8] dog

備註

[Visual Basic 中, C#][Visual Basic, C#]

foreach陳述式的C#語言 (for each在C++, For Each Visual Basic 中) 會隱藏列舉值的複雜度。The foreach statement of the C# language (for each in C++, For Each in Visual Basic) hides the complexity of the enumerators. 因此,建議您使用 foreach,而不要直接使用列舉值。Therefore, using foreach is recommended, instead of directly manipulating the enumerator.

列舉程式可以用來讀取集合中的資料,但是無法用來修改基礎集合。Enumerators can be used to read the data in the collection, but they cannot be used to modify the underlying collection.

一開始,列舉程式位在集合中的第一個項目之前。Initially, the enumerator is positioned before the first element in the collection. Reset 也會將列舉值帶回至這個位置。Reset also brings the enumerator back to this position. 在這個位置上,Current 並未定義。At this position, Current is undefined. 因此,在讀取 MoveNext 的值之前,必須呼叫 Current 以將列舉值前移至集合的第一個項目。Therefore, you must call MoveNext to advance the enumerator to the first element of the collection before reading the value of Current.

Current 會傳回相同的物件直到呼叫 MoveNextResetCurrent returns the same object until either MoveNext or Reset is called. MoveNext 會將 Current 設定為下一個項目。MoveNext sets Current to the next element.

如果MoveNext集合,也就是列舉值的結尾是否位於集合中的最後一個元素之後的階段和MoveNext傳回falseIf MoveNext passes the end of the collection, the enumerator is positioned after the last element in the collection and MoveNext returns false. 列舉值位於此位置,後續呼叫MoveNext也會傳回falseWhen the enumerator is at this position, subsequent calls to MoveNext also return false. 如果上次呼叫MoveNext傳回falseCurrent是未定義。If the last call to MoveNext returned false, Current is undefined. 若要再次將 Current 設定為集合的第一個元素,您可以在呼叫 Reset 之後,接著呼叫 MoveNextTo set Current to the first element of the collection again, you can call Reset followed by MoveNext.

只要集合維持不變,列舉程式就持續有效。An enumerator remains valid as long as the collection remains unchanged. 如果對集合進行變更,例如加入、修改或刪除項目,列舉程式會永久失效,且其行為未定義。If changes are made to the collection, such as adding, modifying, or deleting elements, the enumerator is irrecoverably invalidated and its behavior is undefined.

列舉值對集合並沒有獨佔存取,因此列舉集合在本質上並非安全執行緒的程序。The enumerator does not have exclusive access to the collection; therefore, enumerating through a collection is intrinsically not a thread safe procedure. 若要確保列舉期間的執行緒安全性,您可以在整個列舉期間鎖定集合。To guarantee thread safety during enumeration, you can lock the collection during the entire enumeration. 若要讓多重執行緒能夠存取集合以便進行讀取和寫入,您必須實作自己的同步處理。To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization.

這個方法是 o (1) 作業。This method is an O(1) operation.

適用於