IEnumerable 介面

參考

定義

命名空間:: System.Collections

組件:: System.Runtime.dll

組件:: mscorlib.dll

組件:: netstandard.dll

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。

公開能逐一查看非泛型集合內容一次的列舉程式。

public interface class IEnumerable

public interface IEnumerable

[System.Runtime.InteropServices.Guid("496B0ABE-CDEE-11d3-88E8-00902754C43A")]
public interface IEnumerable

[System.Runtime.InteropServices.Guid("496B0ABE-CDEE-11d3-88E8-00902754C43A")]
[System.Runtime.InteropServices.ComVisible(true)]
public interface IEnumerable

type IEnumerable = interface

[<System.Runtime.InteropServices.Guid("496B0ABE-CDEE-11d3-88E8-00902754C43A")>]
type IEnumerable = interface

[<System.Runtime.InteropServices.Guid("496B0ABE-CDEE-11d3-88E8-00902754C43A")>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type IEnumerable = interface

Public Interface IEnumerable

衍生: Microsoft.Extensions.Configuration.Memory.MemoryConfigurationProvider

Microsoft.Extensions.DependencyInjection.IServiceCollection

Microsoft.Extensions.DependencyInjection.ServiceCollection

Microsoft.Extensions.DiagnosticAdapter.Internal.ProxyEnumerable<TSourceElement,TTargetElement>

Microsoft.Extensions.DiagnosticAdapter.Internal.ProxyList<TSourceElement,TTargetElement>

更多…

屬性: GuidAttribute ComVisibleAttribute

範例

下列程式碼範例示範藉由實 IEnumerable 作和 IEnumerator 介面來逐一查看自訂集合的最佳做法。在此範例中，不會明確呼叫這些介面的成員，但會實作這些介面，以支援 foreach 在 Visual Basic 中使用 (For Each) 逐一查看集合。此範例是完整的主控台應用程式。若要編譯 Visual Basic 應用程式，請在專案的 [屬性] 頁面中，將Startup 物件變更為Sub Main。

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

IEnumerable 是可列舉之所有非泛型集合的基底介面。如需此介面的泛型版本，請參閱 System.Collections.Generic.IEnumerable<T> 。 IEnumerable 包含單一方法， GetEnumerator 這個方法會傳 IEnumerator 回。 IEnumerator藉由公開屬性和方法 MoveNext Reset ，提供逐一 Current 查看集合的能力。

最佳做法是在集合類別上實 IEnumerable 作和 IEnumerator ，以在 Visual Basic) 語法中啟用 foreach (For Each ，但不需要實作 IEnumerable 。如果您的集合未實 IEnumerable 作，您仍必須遵循反覆運算器模式來支援此語法，方法是提供 GetEnumerator 傳回介面、類別或結構的方法。使用 Visual Basic 時，您必須提供 IEnumerator 由傳 GetEnumerator 回的實作。使用 C# 進行開發時，您必須提供類別，其中包含 Current 屬性和 ResetMoveNext 方法，如所述 IEnumerator ，但類別不需要實 IEnumerator 作。

方法

GetEnumerator()

傳回逐一查看集合的列舉值。

擴充方法

Cast<TResult>(IEnumerable)	將 IEnumerable 的項目轉換成指定的型別。
OfType<TResult>(IEnumerable)	根據指定的型別來篩選 IEnumerable 的項目。
AsParallel(IEnumerable)	啟用查詢的平行化作業。
AsQueryable(IEnumerable)	將 IEnumerable 轉換成 IQueryable。

適用於

IEnumerable 介面

定義

範例

備註

方法

擴充方法

適用於

另請參閱

其他資源