List<T>.IEnumerable.GetEnumerator List<T>.IEnumerable.GetEnumerator List<T>.IEnumerable.GetEnumerator Method

定義

傳回逐一查看集合的列舉值。Returns an enumerator that iterates through a collection.

 virtual System::Collections::IEnumerator ^ System.Collections.IEnumerable.GetEnumerator() = System::Collections::IEnumerable::GetEnumerator;
System.Collections.IEnumerator IEnumerable.GetEnumerator ();
Function GetEnumerator () As IEnumerator Implements IEnumerable.GetEnumerator

傳回

IEnumerator,可用於逐一查看集合。An IEnumerator that can be used to iterate through the collection.

實作

備註

foreach for each語言的語句 (在 Visual Basic 中C++ )會隱藏列舉值的複雜度。For Each C#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. 在此位置, Current屬性未定義。At this position, the Current property is undefined. 因此, 在讀取的MoveNext Current值之前, 您必須先呼叫方法, 將枚舉器前移至集合的第一個元素。Therefore, you must call the MoveNext method to advance the enumerator to the first element of the collection before reading the value of Current.

屬性會傳回相同的物件, MoveNext直到呼叫Reset或為止。 CurrentThe Current property 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傳遞集合的結尾, 則列舉值會放置在集合中的最後一個元素之後false, MoveNext並傳回。If MoveNext passes the end of the collection, the enumerator is positioned after the last element in the collection and MoveNext returns false. 當列舉值在此位置時, 後續的呼叫MoveNext false也會傳回。When the enumerator is at this position, subsequent calls to MoveNext also return false. 如果最後一次呼叫MoveNext傳回false, Current則為未定義。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. 如果對集合進行了變更, 例如加入、修改或刪除專案, 枚舉器會失效, 且下一次呼叫MoveNextReset InvalidOperationException會擲回。If changes are made to the collection, such as adding, modifying, or deleting elements, the enumerator is irrecoverably invalidated and the next call to MoveNext or Reset throws an InvalidOperationException.

列舉程式沒有集合的獨佔存取權,因此,列舉集合內容本質上並不是安全的執行緒程序。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.

System.Collections.Generic 命名空間中集合的預設實作未同步處理。Default implementations of collections in the System.Collections.Generic namespace are not synchronized.

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

適用於

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