IEnumerable<T>.GetEnumerator Yöntem

Tanım

Toplulukta yinelenen bir numaralandırıcı döndürür.Returns an enumerator that iterates through the collection.

public:
 System::Collections::Generic::IEnumerator<T> ^ GetEnumerator();
public System.Collections.Generic.IEnumerator<out T> GetEnumerator ();
public System.Collections.Generic.IEnumerator<T> GetEnumerator ();
abstract member GetEnumerator : unit -> System.Collections.Generic.IEnumerator<'T>
Public Function GetEnumerator () As IEnumerator(Of Out T)
Public Function GetEnumerator () As IEnumerator(Of T)

Döndürülenler

IEnumerator<T>

Koleksiyonda yinelemek için kullanılabilecek bir numaralandırıcı.An enumerator that can be used to iterate through the collection.

Örnekler

Aşağıdaki örnek, IEnumerable<T> BIR LINQ sorgusu oluşturmak için arabirimin nasıl uygulanacağını ve bu uygulamayı nasıl kullanacağını gösterir.The following example demonstrates how to implement the IEnumerable<T> interface and uses that implementation to create a LINQ query. Uygulamasını uyguladığınızda, IEnumerable<T> veya ' i de uygulamanız gerekir, IEnumerator<T> yalnızca C# için yield anahtar sözcüğünü kullanabilirsiniz.When you implement IEnumerable<T>, you must also implement IEnumerator<T> or, for C# only, you can use the yield keyword. IEnumerator<T>Ayrıca IDisposable , bu örnekte göreceğiniz gibi uygulanması gerekir.Implementing IEnumerator<T> also requires IDisposable to be implemented, which you will see in this example.

using System;
using System.IO;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

public class App
{
    // Excercise the Iterator and show that it's more
    // performant.
    public static void Main()
    {
        TestStreamReaderEnumerable();
        Console.WriteLine("---");
        TestReadingFile();
    }

    public static void TestStreamReaderEnumerable()
    {
        // Check the memory before the iterator is used.
        long memoryBefore = GC.GetTotalMemory(true);
      IEnumerable<String> stringsFound;
        // Open a file with the StreamReaderEnumerable and check for a string.
      try {
         stringsFound =
               from line in new StreamReaderEnumerable(@"c:\temp\tempFile.txt")
               where line.Contains("string to search for")
               select line;
         Console.WriteLine("Found: " + stringsFound.Count());
      }
      catch (FileNotFoundException) {
         Console.WriteLine(@"This example requires a file named C:\temp\tempFile.txt.");
         return;
      }

        // Check the memory after the iterator and output it to the console.
        long memoryAfter = GC.GetTotalMemory(false);
        Console.WriteLine("Memory Used With Iterator = \t"
            + string.Format(((memoryAfter - memoryBefore) / 1000).ToString(), "n") + "kb");
    }

    public static void TestReadingFile()
    {
        long memoryBefore = GC.GetTotalMemory(true);
      StreamReader sr;
      try {
         sr = File.OpenText("c:\\temp\\tempFile.txt");
      }
      catch (FileNotFoundException) {
         Console.WriteLine(@"This example requires a file named C:\temp\tempFile.txt.");
         return;
      }

        // Add the file contents to a generic list of strings.
        List<string> fileContents = new List<string>();
        while (!sr.EndOfStream) {
            fileContents.Add(sr.ReadLine());
        }

        // Check for the string.
        var stringsFound =
            from line in fileContents
            where line.Contains("string to search for")
            select line;

        sr.Close();
        Console.WriteLine("Found: " + stringsFound.Count());

        // Check the memory after when the iterator is not used, and output it to the console.
        long memoryAfter = GC.GetTotalMemory(false);
        Console.WriteLine("Memory Used Without Iterator = \t" +
            string.Format(((memoryAfter - memoryBefore) / 1000).ToString(), "n") + "kb");
    }
}

// A custom class that implements IEnumerable(T). When you implement IEnumerable(T),
// you must also implement IEnumerable and IEnumerator(T).
public class StreamReaderEnumerable : IEnumerable<string>
{
    private string _filePath;
    public StreamReaderEnumerable(string filePath)
    {
        _filePath = filePath;
    }

    // Must implement GetEnumerator, which returns a new StreamReaderEnumerator.
    public IEnumerator<string> GetEnumerator()
    {
        return new StreamReaderEnumerator(_filePath);
    }

    // Must also implement IEnumerable.GetEnumerator, but implement as a private method.
    private IEnumerator GetEnumerator1()
    {
        return this.GetEnumerator();
    }
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator1();
    }
}

// When you implement IEnumerable(T), you must also implement IEnumerator(T),
// which will walk through the contents of the file one line at a time.
// Implementing IEnumerator(T) requires that you implement IEnumerator and IDisposable.
public class StreamReaderEnumerator : IEnumerator<string>
{
    private StreamReader _sr;
    public StreamReaderEnumerator(string filePath)
    {
        _sr = new StreamReader(filePath);
    }

    private string _current;
    // Implement the IEnumerator(T).Current publicly, but implement
    // IEnumerator.Current, which is also required, privately.
    public string Current
    {

        get
        {
            if (_sr == null || _current == null)
            {
                throw new InvalidOperationException();
            }

            return _current;
        }
    }

    private object Current1
    {

        get { return this.Current; }
    }

    object IEnumerator.Current
    {
        get { return Current1; }
    }

    // Implement MoveNext and Reset, which are required by IEnumerator.
    public bool MoveNext()
    {
        _current = _sr.ReadLine();
        if (_current == null)
            return false;
        return true;
    }

    public void Reset()
    {
        _sr.DiscardBufferedData();
        _sr.BaseStream.Seek(0, SeekOrigin.Begin);
        _current = null;
    }

    // Implement IDisposable, which is also implemented by IEnumerator(T).
    private bool disposedValue = false;
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        if (!this.disposedValue)
        {
            if (disposing)
            {
                // Dispose of managed resources.
            }
            _current = null;
            if (_sr != null) {
               _sr.Close();
               _sr.Dispose();
            }
        }

        this.disposedValue = true;
    }

     ~StreamReaderEnumerator()
    {
        Dispose(false);
    }
}
// This example displays output similar to the following:
//       Found: 2
//       Memory Used With Iterator =     33kb
//       ---
//       Found: 2
//       Memory Used Without Iterator =  206kb
Imports System.IO
Imports System.Collections
Imports System.Collections.Generic
Imports System.Linq

Public Module App
   ' Excercise the Iterator and show that it's more performant.
   Public Sub Main()
      TestStreamReaderEnumerable()
      Console.WriteLine("---")
      TestReadingFile()
   End Sub

   Public Sub TestStreamReaderEnumerable()
        ' Check the memory before the iterator is used.
        Dim memoryBefore As Long = GC.GetTotalMemory(true)
      Dim stringsFound As IEnumerable(Of String)
        ' Open a file with the StreamReaderEnumerable and check for a string.
      Try
         stringsFound =
               from line in new StreamReaderEnumerable("c:\temp\tempFile.txt")
               where line.Contains("string to search for")
               select line
         Console.WriteLine("Found: {0}", stringsFound.Count())
      Catch e As FileNotFoundException
         Console.WriteLine("This example requires a file named C:\temp\tempFile.txt.")
         Return
      End Try

        ' Check the memory after the iterator and output it to the console.
        Dim memoryAfter As Long = GC.GetTotalMemory(false)
        Console.WriteLine("Memory Used with Iterator = {1}{0} kb",
                        (memoryAfter - memoryBefore)\1000, vbTab)
   End Sub

   Public Sub TestReadingFile()
        Dim memoryBefore As Long = GC.GetTotalMemory(true)
      Dim sr As StreamReader
      Try
         sr = File.OpenText("c:\temp\tempFile.txt")
      Catch e As FileNotFoundException
         Console.WriteLine("This example requires a file named C:\temp\tempFile.txt.")
         Return
      End Try

        ' Add the file contents to a generic list of strings.
        Dim fileContents As New List(Of String)()
        Do While Not sr.EndOfStream
            fileContents.Add(sr.ReadLine())
      Loop

        ' Check for the string.
        Dim stringsFound =
            from line in fileContents
            where line.Contains("string to search for")
            select line

      sr.Close()
      Console.WriteLine("Found: {0}", stringsFound.Count())

        ' Check the memory after when the iterator is not used, and output it to the console.
        Dim memoryAfter As Long = GC.GetTotalMemory(False)
        Console.WriteLine("Memory Used without Iterator = {1}{0} kb",
                        (memoryAfter - memoryBefore)\1000, vbTab)
   End Sub
End Module

' A custom class that implements IEnumerable(T). When you implement IEnumerable(T), 
' you must also implement IEnumerable and IEnumerator(T).
Public Class StreamReaderEnumerable : Implements IEnumerable(Of String)
    Private _filePath As String
    
    Public Sub New(filePath As String)
        _filePath = filePath
    End Sub

    ' Must implement GetEnumerator, which returns a new StreamReaderEnumerator.
    Public Function GetEnumerator() As IEnumerator(Of String) _
          Implements IEnumerable(Of String).GetEnumerator
        Return New StreamReaderEnumerator(_filePath)
    End Function

    ' Must also implement IEnumerable.GetEnumerator, but implement as a private method.
    Private Function GetEnumerator1() As IEnumerator _
          Implements IEnumerable.GetEnumerator
        Return Me.GetEnumerator()
    End Function
End Class

' When you implement IEnumerable(T), you must also implement IEnumerator(T), 
' which will walk through the contents of the file one line at a time.
' Implementing IEnumerator(T) requires that you implement IEnumerator and IDisposable.
Public Class StreamReaderEnumerator : Implements IEnumerator(Of String)
    Private _sr As StreamReader
    
    Public Sub New(filePath As String)
        _sr = New StreamReader(filePath)
    End Sub

    Private _current As String

    ' Implement the IEnumerator(T).Current Publicly, but implement 
    ' IEnumerator.Current, which is also required, privately.
    Public ReadOnly Property Current As String _
          Implements IEnumerator(Of String).Current
        Get
            If _sr Is Nothing OrElse _current Is Nothing
                Throw New InvalidOperationException()
            End If

            Return _current
        End Get
    End Property

    Private ReadOnly Property Current1 As Object _
          Implements IEnumerator.Current
        Get
           Return Me.Current
        End Get
    End Property

    ' Implement MoveNext and Reset, which are required by IEnumerator.
    Public Function MoveNext() As Boolean _
          Implements IEnumerator.MoveNext
        _current = _sr.ReadLine()
        if _current Is Nothing Then Return False

        Return True
    End Function

    Public Sub Reset() _
          Implements IEnumerator.Reset
        _sr.DiscardBufferedData()
        _sr.BaseStream.Seek(0, SeekOrigin.Begin)
        _current = Nothing
    End Sub

    ' Implement IDisposable, which is also implemented by IEnumerator(T).
    Private disposedValue As Boolean = False
    Public Sub Dispose() _
          Implements IDisposable.Dispose
        Dispose(True)
        GC.SuppressFinalize(Me)
    End Sub

    Protected Overridable Sub Dispose(disposing As Boolean)
        If Not Me.disposedValue Then
            If disposing Then
                ' Dispose of managed resources.
            End If

            _current = Nothing
            If _sr IsNot Nothing Then
               _sr.Close()
               _sr.Dispose()
            End If
        End If

        Me.disposedValue = True
    End Sub

    Protected Overrides Sub Finalize()
        Dispose(False)
    End Sub
End Class
' This example displays output similar to the following:
'       Found: 2
'       Memory Used With Iterator =     33kb
'       ---
'       Found: 2
'       Memory Used Without Iterator =  206kb

Arabirimin nasıl uygulanacağını gösteren başka bir C# örneği için IEnumerable<T> bkz. Genel türler örneği.For another C# example that demonstrates how to implement the IEnumerable<T> interface, see the Generics Sample. Bu örnek, yield uygulamak yerine anahtar sözcüğünün kullanır IEnumerator<T> .This sample uses of the yield keyword instead of implementing IEnumerator<T>.

Açıklamalar

Döndürülen, IEnumerator<T> bir özelliği ortaya çıkaran koleksiyonda yineleme yapabilme yeteneği sağlar Current . Bir koleksiyondaki verileri okumak için numaralandırıcıları kullanabilirsiniz, ancak koleksiyonu değiştiremezsiniz.The returned IEnumerator<T> provides the ability to iterate through the collection by exposing a Current property .You can use enumerators to read the data in a collection, but not to modify the collection.

Başlangıçta, numaralandırıcı, koleksiyondaki ilk öğenin önüne yerleştirilir.Initially, the enumerator is positioned before the first element in the collection. Bu konumda Current tanımsız.At this position, Current is undefined. Bu nedenle, MoveNext değerini okumadan önce sayacı koleksiyonun ilk öğesine ilerletmek için yöntemini çağırmanız gerekir Current .Therefore, you must call the MoveNext method to advance the enumerator to the first element of the collection before reading the value of Current.

CurrentMoveNextNext öğesine kümeler olarak yeniden çağrılıncaya kadar aynı nesneyi döndürür MoveNext Current .Current returns the same object until MoveNext is called again as MoveNext sets Current to the next element.

MoveNextKoleksiyonun sonunu geçerse, Numaralandırıcı koleksiyondaki son öğeden sonra konumlandırılır ve MoveNext döndürür false .If MoveNext passes the end of the collection, the enumerator is positioned after the last element in the collection and MoveNext returns false. Numaralandırıcı bu konumda olduğunda, sonraki çağrılar MoveNext de döndürülür false .When the enumerator is at this position, subsequent calls to MoveNext also return false. Döndürülen son çağrı MoveNext false Current tanımsızdır.If the last call to MoveNext returned false, Current is undefined. CurrentKoleksiyonun ilk öğesine yeniden ayarlayamazsınız. bunun yerine yeni bir Numaralandırıcı örneği oluşturmanız gerekir.You cannot set Current to the first element of the collection again; you must create a new enumerator instance instead.

Koleksiyonda değişiklik yapılırsa (öğe ekleme, değiştirme veya silme gibi), Numaralandırıcının davranışı tanımsızdır.If changes are made to the collection, such as adding, modifying, or deleting elements, the behavior of the enumerator is undefined.

Numaralandırıcı, koleksiyon değişmeden kaldığı sürece bir Numaralandırıcı geçerli kalacak şekilde koleksiyona özel erişime sahip değildir.An enumerator does not have exclusive access to the collection so an enumerator remains valid as long as the collection remains unchanged. Koleksiyonda değişiklik yapılırsa (öğe ekleme, değiştirme veya silme gibi), numaralandırıcı geçersiz kılınır ve beklenmedik sonuçlar elde edebilirsiniz.If changes are made to the collection, such as adding, modifying, or deleting elements, the enumerator is invalidated and you may get unexpected results. Ayrıca, bir koleksiyonun numaralandırılması iş parçacığı güvenli bir yordam değildir.Also, enumerating a collection is not a thread-safe procedure. İş parçacığı güvenliğini güvence altına almak için, Numaralandırıcı sırasında koleksiyonu kilitlemeniz veya koleksiyonda eşitleme uygulamanız gerekir.To guarantee thread-safety, you should lock the collection during enumerator or implement synchronization on the collection.

Ad alanındaki koleksiyonların varsayılan uygulamaları System.Collections.Generic eşitlenmez.Default implementations of collections in the System.Collections.Generic namespace aren't synchronized.

Şunlara uygulanır

Ayrıca bkz.