HashSet<T>.Enumerator 結構

定義

列舉 HashSet<T> 物件的項目。Enumerates the elements of a HashSet<T> object.

public: value class HashSet<T>::Enumerator : System::Collections::Generic::IEnumerator<T>
[System.Serializable]
public struct HashSet<T>.Enumerator : System.Collections.Generic.IEnumerator<T>
type HashSet<'T>.Enumerator = struct
    interface IEnumerator<'T>
    interface IEnumerator
    interface IDisposable
Public Structure HashSet(Of T).Enumerator
Implements IEnumerator(Of T)

類型參數

T
繼承
HashSet<T>.Enumerator
屬性
實作

備註

foreach for each語言的語句 (在 Visual Basic 中C++ )會隱藏枚舉器的複雜度。For Each C#The foreach statement of the C# language (for each in C++, For Each in Visual Basic) hides the complexity of 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. 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.

Current 會傳回相同的物件直到呼叫 MoveNextCurrent returns the same object until MoveNext 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. 您不能Current再次將設定為集合的第一個元素; 您必須改為建立新的列舉值物件。You cannot set Current to the first element of the collection again; you must create a new enumerator object instead.

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MoveNextIEnumerator.Reset 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 IEnumerator.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.

屬性

Current

取得位於目前列舉值位置的項目。Gets the element at the current position of the enumerator.

方法

Dispose()

釋放由 HashSet<T>.Enumerator 物件使用的所有資源。Releases all resources used by a HashSet<T>.Enumerator object.

MoveNext()

讓列舉程式前進至 HashSet<T> 集合中的下一個項目。Advances the enumerator to the next element of the HashSet<T> collection.

明確介面實作

IEnumerator.Current

取得位於目前列舉值位置的項目。Gets the element at the current position of the enumerator.

IEnumerator.Reset()

設定列舉值至它的初始位置,這是在集合中第一個項目之前。Sets the enumerator to its initial position, which is before the first element in the collection.

適用於