ReadOnlyCollection<T>.IEnumerable.GetEnumerator ReadOnlyCollection<T>.IEnumerable.GetEnumerator ReadOnlyCollection<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

C#語言foreach的語句for each C++Visual中為VisualBasic)會隱藏列舉值的複雜度。For EachThe foreach statement of the C# language (for each in Visual 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集合的預設實值不會同步處理。Default implementations of collections in System.Collections.Generic are not synchronized.

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

這個成員是明確介面成員實作,This member is an explicit interface member implementation. 只有在 ReadOnlyCollection<T> 執行個體轉換成 IEnumerable 介面時,才能使用這個成員。It can be used only when the ReadOnlyCollection<T> instance is cast to an IEnumerable interface.

適用於

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