IEnumerator.Current 屬性

定義

命名空間:

System.Collections

組件:

System.Runtime.dll

取得集合中位於列舉值目前位置的元素。

public:
 property System::Object ^ Current { System::Object ^ get(); };

public object Current { get; }

member this.Current : obj

Public ReadOnly Property Current As Object

屬性值

Object

位於列舉值中目前位置的集合中的元素。

範例

下列程式代碼範例示範自定義集合介面的 IEnumerator 實作。 在此範例中， Current 不會明確呼叫 ，但會實作以支援在Visual Basic) 中使用 foreach (for each 。 此程式代碼範例是介面較大範例的 IEnumerator 一部分。

// When you implement IEnumerable, you must also implement IEnumerator.
public class PeopleEnum : IEnumerator
{
    public Person[] _people;

    // Enumerators are positioned before the first element
    // until the first MoveNext() call.
    int position = -1;

    public PeopleEnum(Person[] list)
    {
        _people = list;
    }

    public bool MoveNext()
    {
        position++;
        return (position < _people.Length);
    }

    public void Reset()
    {
        position = -1;
    }

    object IEnumerator.Current
    {
        get
        {
            return Current;
        }
    }

    public Person Current
    {
        get
        {
            try
            {
                return _people[position];
            }
            catch (IndexOutOfRangeException)
            {
                throw new InvalidOperationException();
            }
        }
    }
}

' When you implement IEnumerable, you must also implement IEnumerator.
Public Class PeopleEnum
    Implements IEnumerator

    Public _people() As Person

    ' Enumerators are positioned before the first element
    ' until the first MoveNext() call.
    Dim position As Integer = -1

    Public Sub New(ByVal list() As Person)
        _people = list
    End Sub

    Public Function MoveNext() As Boolean Implements IEnumerator.MoveNext
        position = position + 1
        Return (position < _people.Length)
    End Function

    Public Sub Reset() Implements IEnumerator.Reset
        position = -1
    End Sub

    Public ReadOnly Property Current() As Object Implements IEnumerator.Current
        Get
            Try
                Return _people(position)
            Catch ex As IndexOutOfRangeException
                Throw New InvalidOperationException()
            End Try
        End Get
    End Property
End Class

備註

Current 在下列任一情況下未定義：

• 列舉值位於集合中的第一個專案之前，緊接在建立列舉值之後。 MoveNext 必須先呼叫 ，才能將列舉值前移至集合的第一個專案，才能讀取的值 Current。

• 最後一 MoveNext 次呼叫傳 false回的 ，表示集合的結尾。

• 列舉值因為集合中所做的變更而失效，例如新增、修改或刪除專案。

Current 會傳回相同的物件直到呼叫 MoveNext。 MoveNext 會將 Current 設定為下一個項目。

另請參閱

• MoveNext()
• Reset()