IEnumerable<t> 接口 (System.Collections.Generic)

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generic <typename T>
public interface class IEnumerable : System::Collections::IEnumerable

public interface IEnumerable<out T> : System.Collections.IEnumerable

public interface IEnumerable<T> : System.Collections.IEnumerable

type seq<'T> = interface
    interface IEnumerable

Public Interface IEnumerable(Of Out T)
Implements IEnumerable

Public Interface IEnumerable(Of T)
Implements IEnumerable

以下示例演示如何实现 IEnumerable<T> 接口以及如何使用该实现来创建 LINQ 查询。实现 IEnumerable<T> 时，还必须实现 IEnumerator<T> 或，仅对于 C#，可以使用 yield 关键字。实现 IEnumerator<T> 还需要 IDisposable 实现，你将在本示例中看到这一点。


   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
            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(disposing: 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(disposing: 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.
         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
         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())
        ' 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
            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
           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(disposing:=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(disposing:=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
    
     
      IEnumerable<T>
     
     是 命名空间中
     
      System.Collections.Generic
     
     集合（例如 、
     
      Dictionary<TKey,TValue>
     
     和
     
      Stack<T>
     
     ）
     
      List<T>
     
     和其他泛型集合（如
     
      ObservableCollection<T>
     
     和
     
      ConcurrentStack<T>
     
     ）的基接口。 可以使用 语句枚举实现
     
      IEnumerable<T>
     
     的
     
      foreach
     
     集合。
    
    
     有关此接口的非泛型版本，请参阅
     
      System.Collections.IEnumerable
     
     。
    
    
     
      IEnumerable<T>
     
     包含实现此接口时必须实现的单个方法;
     
      GetEnumerator
     
     ，返回
     
      IEnumerator<T>
     
     对象。 返回的
     
      IEnumerator<T>
     
     提供通过公开
     
      Current
     
     属性循环访问集合的功能。
    
    
     实施者说明
    
    
     为了保持与循环访问非泛型集合的方法兼容，
     
      IEnumerable<T>
     
     实现
     
      IEnumerable
     
     。 这允许将泛型集合传递到需要对象
     
      IEnumerable
     
     的方法。
    
    
     ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>,
 Func<TSource,TKey>, Func<TSource,TValue>, IEqualityComparer<TKey>,
 IEqualityComparer<TValue>)
    
    
     枚举并转换序列，然后使用指定的键和值比较器生成其内容的不可变字典。
    
    
     GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,
TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,
TResult>, IEqualityComparer<TKey>)
    
    
     根据指定的键选择器函数对序列中的元素进行分组，并且从每个组及其键中创建结果值。 通过使用指定的比较器对键值进行比较，并且通过使用指定的函数对每个组的元素进行投影。
    
    
     GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>,
 Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>,
TResult>)
    
    
     基于键值等同性对两个序列的元素进行关联，并对结果进行分组。 使用默认的相等比较器对键进行比较。
    
    
     GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>,
 Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>,
TResult>, IEqualityComparer<TKey>)
    
    
     基于键值等同性对两个序列的元素进行关联，并对结果进行分组。 使用指定的
     
      IEqualityComparer<T>
     
     对键进行比较。
    
    
     Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>,
 Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>,
 IEqualityComparer<TKey>)
    
    
     基于匹配键对两个序列的元素进行关联。 使用指定的
     
      IEqualityComparer<T>
     
     对键进行比较。