IEnumerator 介面

定義

命名空間:: System.Collections

組件:: mscorlib.dll, System.Runtime.dll

組件:: netstandard.dll, System.Runtime.dll

組件:: System.Runtime.dll

組件:: mscorlib.dll

組件:: netstandard.dll

來源:: IEnumerator.cs

來源:: IEnumerator.cs

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

支援非泛型集合上的簡單反覆專案。

public interface class IEnumerator

public interface IEnumerator

[System.Runtime.InteropServices.Guid("496B0ABF-CDEE-11d3-88E8-00902754C43A")]
public interface IEnumerator

[System.Runtime.InteropServices.Guid("496B0ABF-CDEE-11d3-88E8-00902754C43A")]
[System.Runtime.InteropServices.ComVisible(true)]
public interface IEnumerator

type IEnumerator = interface

[<System.Runtime.InteropServices.Guid("496B0ABF-CDEE-11d3-88E8-00902754C43A")>]
type IEnumerator = interface

[<System.Runtime.InteropServices.Guid("496B0ABF-CDEE-11d3-88E8-00902754C43A")>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type IEnumerator = interface

Public Interface IEnumerator

衍生: Microsoft.Extensions.AI.AdditionalPropertiesDictionary<TValue>.Enumerator

Microsoft.Extensions.Primitives.StringTokenizer.Enumerator

Microsoft.Extensions.Primitives.StringValues.Enumerator

Microsoft.VisualBasic.Compatibility.VB6.BindingCollectionEnumerator

Microsoft.VisualBasic.Vsa.VsaItemsEnumerator

更多…

屬性: GuidAttribute ComVisibleAttribute

範例

以下程式碼範例展示了自訂集合中 IEnumerable 和 IEnumerator 介面的實作。在此範例中，這些介面的成員並未被明確呼叫，但它們實作以支援在 Visualforeach Basic 中以for each遍歷集合。

using System;
using System.Collections;

// Simple business object.
public class Person
{
    public Person(string fName, string lName)
    {
        this.firstName = fName;
        this.lastName = lName;
    }

    public string firstName;
    public string lastName;
}

// Collection of Person objects. This class
// implements IEnumerable so that it can be used
// with ForEach syntax.
public class People : IEnumerable
{
    private Person[] _people;
    public People(Person[] pArray)
    {
        _people = new Person[pArray.Length];

        for (int i = 0; i < pArray.Length; i++)
        {
            _people[i] = pArray[i];
        }
    }

// Implementation for the GetEnumerator method.
    IEnumerator IEnumerable.GetEnumerator()
    {
       return (IEnumerator) GetEnumerator();
    }

    public PeopleEnum GetEnumerator()
    {
        return new PeopleEnum(_people);
    }
}

// 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();
            }
        }
    }
}

class App
{
    static void Main()
    {
        Person[] peopleArray = new Person[3]
        {
            new Person("John", "Smith"),
            new Person("Jim", "Johnson"),
            new Person("Sue", "Rabon"),
        };

        People peopleList = new People(peopleArray);
        foreach (Person p in peopleList)
            Console.WriteLine(p.firstName + " " + p.lastName);
    }
}

/* This code produces output similar to the following:
 *
 * John Smith
 * Jim Johnson
 * Sue Rabon
 *
 */

Imports System.Collections

' Simple business object.
Public Class Person

    Public Sub New(ByVal fName As String, ByVal lName As String)
        Me.firstName = fName
        Me.lastName = lName
    End Sub


    Public firstName As String
    Public lastName As String
End Class

' Collection of Person objects, which implements IEnumerable so that
' it can be used with ForEach syntax.
Public Class People
    Implements IEnumerable

    Private _people() As Person

    Public Sub New(ByVal pArray() As Person)
        _people = New Person(pArray.Length - 1) {}

        Dim i As Integer
        For i = 0 To pArray.Length - 1
            _people(i) = pArray(i)
        Next i
    End Sub

    ' Implementation of GetEnumerator.
    Public Function GetEnumerator() As IEnumerator _
      Implements IEnumerable.GetEnumerator

        Return New PeopleEnum(_people)
    End Function

End Class

' 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

Class App
    Shared Sub Main()
        Dim peopleArray() As Person = { _
            New Person("John", "Smith"), _
            New Person("Jim", "Johnson"), _
            New Person("Sue", "Rabon")}

        Dim peopleList As New People(peopleArray)
        Dim p As Person
        For Each p In peopleList
            Console.WriteLine(p.firstName + " " + p.lastName)
        Next

    End Sub
End Class

' This code produces output similar to the following:
' 
' John Smith
' Jim Johnson
' Sue Rabon

備註

IEnumerator 是所有非通用列舉器的基礎介面。它的通用對應物是 System.Collections.Generic.IEnumerator<T> 介面。

foreach C# 語言（for each在 Visual Basic 中）的陳述隱藏了列舉器的複雜度。因此，建議使用 foreach 而非直接操作普查器。

列舉值可用來讀取集合中的數據，但無法用來修改基礎集合。

此 Reset 方法旨在實現 COM 互通性，且不必完全實作;實作者可以拋出 NotSupportedException。

一開始，列舉值會放在集合中的第一個專案之前。你必須呼叫 MoveNext 方法將列舉子推進到集合的第一個元素，才能讀取 Current;否則 Current 是未定義的。

Current 回傳相同物件，直到被呼叫其中一 MoveNext 或 Reset 。 MoveNext 設定 Current 為下一個元素。

若 MoveNext 通過集合的末尾，列舉器會位於集合的最後一個元素之後，並 MoveNext 返回 false。當列舉器處於此位置時，後續呼叫 MoveNext 也返回 false。若最後一次呼叫 MoveNext 回傳 false， Current 則為未定義。

若要再次設定 Current 為集合的第一個元素，你可以呼叫 Reset，如果有實作，接 MoveNext著。如果 Reset 沒有實作，你必須建立一個新的列舉器實例，才能回到集合的第一個元素。

如果對集合進行變更，例如新增、修改或刪除專案，列舉值的行為是未定義的。

列舉值沒有集合的獨佔存取權;因此，透過集合列舉本質上不是安全線程的程式。即使集合同步處理，其他線程仍然可以修改集合，這會導致列舉值擲回例外狀況。若要保證列舉期間的線程安全性，您可以在整個列舉期間鎖定集合，或攔截其他線程所做的變更所產生的例外狀況。

屬性

名稱	Description
Current	取得集合中位於列舉值目前位置的專案。

方法

名稱	Description
MoveNext()	將列舉值前進至集合的下一個專案。
Reset()	將列舉值設定為其初始位置，也就是集合中第一個專案之前。

適用於

另請參閱

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IEnumerator 介面

定義

範例

備註

屬性

方法

適用於

另請參閱

意見反應