IEnumerable<T> IEnumerable<T> IEnumerable<T> IEnumerable<T> Interface

定義

公開支援指定型別集合上簡單反覆運算的列舉值。Exposes the enumerator, which supports a simple iteration over a collection of a specified type.

generic <typename T>
public interface class IEnumerable : System::Collections::IEnumerable
public interface IEnumerable<out T> : System.Collections.IEnumerable
type seq<'T> = interface
    interface IEnumerable
Public Interface IEnumerable(Of Out T)
Implements IEnumerable

類型參數

T

要列舉之物件的型別。The type of objects to enumerate.

衍生
實作

範例

下列範例示範如何實作IEnumerable<T>介面,以及如何使用這個實作來建立 LINQ 查詢。The following example demonstrates how to implement the IEnumerable<T> interface and how to use that implementation to create a LINQ query. 當您實作IEnumerable<T>,您也必須實作IEnumerator<T>或僅適用 C#,您可以使用產生關鍵字。When you implement IEnumerable<T>, you must also implement IEnumerator<T> or, for C# only, you can use the yield keyword. 實作IEnumerator<T>也需要IDisposable實作,您就會在此範例中看到。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

如需其他 C# 範例示範如何實作IEnumerable<T>介面,請參閱 < 泛型範例For another C# example that demonstrates how to implement the IEnumerable<T> interface, see the Generics Sample. 這個範例會使用yield關鍵字,而不實作IEnumerator<T>This sample uses the yield keyword instead of implementing IEnumerator<T>.

備註

IEnumerable<T> 在為集合的基底介面System.Collections.Generic命名空間,例如List<T>Dictionary<TKey,TValue>,和Stack<T>與其他泛型集合,例如ObservableCollection<T>ConcurrentStack<T>IEnumerable<T> is the base interface for collections in the System.Collections.Generic namespace such as List<T>, Dictionary<TKey,TValue>, and Stack<T> and other generic collections such as ObservableCollection<T> and ConcurrentStack<T>. 實作的集合IEnumerable<T>可以藉由使用列舉foreach陳述式。Collections that implement IEnumerable<T> can be enumerated by using the foreach statement.

這個介面的非泛型版本,請參閱System.Collections.IEnumerableFor the non-generic version of this interface, see System.Collections.IEnumerable.

IEnumerable<T> 包含實作此介面; 時,您必須實作單一方法GetEnumerator,以傳回IEnumerator<T>物件。IEnumerable<T> contains a single method that you must implement when implementing this interface; GetEnumerator, which returns an IEnumerator<T> object. 傳回IEnumerator<T>讓您能夠藉由公開逐一查看集合Current屬性。The returned IEnumerator<T> provides the ability to iterate through the collection by exposing a Current property.

給實施者的注意事項

System.Collections.Generic.IEnumerable\`1 功能同位檢查與非泛型集合;實作System.Collections.Generic.IEnumerable\`1可讓要傳遞至預期的方法的泛型集合IEnumerable物件。 System.Collections.Generic.IEnumerable\`1 is included for parity with non-generic collections; implementing System.Collections.Generic.IEnumerable\`1 allows a generic collection to be passed to a method that expects an IEnumerable object.

方法

GetEnumerator() GetEnumerator() GetEnumerator() GetEnumerator()

傳回逐一查看集合的列舉值。Returns an enumerator that iterates through the collection.

Extension Methods

CopyToDataTable<T>(IEnumerable<T>) CopyToDataTable<T>(IEnumerable<T>) CopyToDataTable<T>(IEnumerable<T>) CopyToDataTable<T>(IEnumerable<T>)

傳回DataTable,其中包含副本DataRow物件,指定輸入IEnumerable<T>物件其中泛型參數TDataRowReturns a DataTable that contains copies of the DataRow objects, given an input IEnumerable<T> object where the generic parameter T is DataRow.

CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption)

複本DataRow至指定的物件DataTable,根據輸入IEnumerable<T>物件其中泛型參數TDataRowCopies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.

CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler)

複本DataRow至指定的物件DataTable,根據輸入IEnumerable<T>物件其中泛型參數TDataRowCopies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.

Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable)

IEnumerable 的項目轉換成指定的型別。Casts the elements of an IEnumerable to the specified type.

OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable)

篩選的項目IEnumerable根據指定的型別。Filters the elements of an IEnumerable based on a specified type.

AsParallel(IEnumerable) AsParallel(IEnumerable) AsParallel(IEnumerable) AsParallel(IEnumerable)

啟用查詢的平行化作業。Enables parallelization of a query.

AsQueryable(IEnumerable) AsQueryable(IEnumerable) AsQueryable(IEnumerable) AsQueryable(IEnumerable)

將轉換IEnumerableIQueryableConverts an IEnumerable to an IQueryable.

Ancestors<T>(IEnumerable<T>) Ancestors<T>(IEnumerable<T>) Ancestors<T>(IEnumerable<T>) Ancestors<T>(IEnumerable<T>)

傳回包含來源集合中每個節點祖系的項目集合。Returns a collection of elements that contains the ancestors of every node in the source collection.

Ancestors<T>(IEnumerable<T>, XName) Ancestors<T>(IEnumerable<T>, XName) Ancestors<T>(IEnumerable<T>, XName) Ancestors<T>(IEnumerable<T>, XName)

傳回包含來源集合中每個節點祖系的已篩選項目集合。Returns a filtered collection of elements that contains the ancestors of every node in the source collection. 集合中只會包含具有相符之 XName 的項目。Only elements that have a matching XName are included in the collection.

DescendantNodes<T>(IEnumerable<T>) DescendantNodes<T>(IEnumerable<T>) DescendantNodes<T>(IEnumerable<T>) DescendantNodes<T>(IEnumerable<T>)

傳回來源集合中每個文件和項目之子代節點的集合。Returns a collection of the descendant nodes of every document and element in the source collection.

Descendants<T>(IEnumerable<T>) Descendants<T>(IEnumerable<T>) Descendants<T>(IEnumerable<T>) Descendants<T>(IEnumerable<T>)

傳回包含來源集合中每個項目和文件之子代項目的項目集合。Returns a collection of elements that contains the descendant elements of every element and document in the source collection.

Descendants<T>(IEnumerable<T>, XName) Descendants<T>(IEnumerable<T>, XName) Descendants<T>(IEnumerable<T>, XName) Descendants<T>(IEnumerable<T>, XName)

傳回已篩選的項目集合,其中包含來源集合中每個項目和文件的子代項目。Returns a filtered collection of elements that contains the descendant elements of every element and document in the source collection. 集合中只會包含具有相符之 XName 的項目。Only elements that have a matching XName are included in the collection.

Elements<T>(IEnumerable<T>) Elements<T>(IEnumerable<T>) Elements<T>(IEnumerable<T>) Elements<T>(IEnumerable<T>)

傳回來源集合中每個項目和文件的子項目集合。Returns a collection of the child elements of every element and document in the source collection.

Elements<T>(IEnumerable<T>, XName) Elements<T>(IEnumerable<T>, XName) Elements<T>(IEnumerable<T>, XName) Elements<T>(IEnumerable<T>, XName)

傳回來源集合中每個項目和文件的已篩選子項目集合。Returns a filtered collection of the child elements of every element and document in the source collection. 集合中只會包含具有相符之 XName 的項目。Only elements that have a matching XName are included in the collection.

InDocumentOrder<T>(IEnumerable<T>) InDocumentOrder<T>(IEnumerable<T>) InDocumentOrder<T>(IEnumerable<T>) InDocumentOrder<T>(IEnumerable<T>)

傳回包含來源集合中所有節點的節點集合,依據文件順序來排序。Returns a collection of nodes that contains all nodes in the source collection, sorted in document order.

Nodes<T>(IEnumerable<T>) Nodes<T>(IEnumerable<T>) Nodes<T>(IEnumerable<T>) Nodes<T>(IEnumerable<T>)

傳回來源集合中每個文件和項目的子節點集合。Returns a collection of the child nodes of every document and element in the source collection.

Remove<T>(IEnumerable<T>) Remove<T>(IEnumerable<T>) Remove<T>(IEnumerable<T>) Remove<T>(IEnumerable<T>)

在來源集合中,從每一個節點的父節點移除這些節點。Removes every node in the source collection from its parent node.

適用於

另請參閱