I​Enumerable<​T> Interface

Definition

Exposes the enumerator, which supports a simple iteration over a collection of a specified type.

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

The type of objects to enumerate.

Derived
Implements

Examples

The following example demonstrates how to implement the IEnumerable<T> interface and how to use that implementation to create a LINQ query. When you implement IEnumerable<T>, you must also implement IEnumerator<T> or, for C# only, you can use the yield keyword. 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

For another C# example that demonstrates how to implement the IEnumerable<T> interface, see the Generics Sample. This sample uses the yield keyword instead of implementing IEnumerator<T>.

Remarks

Note

To view the .NET Framework source code for this type, see the Reference Source. You can browse through the source code online, download the reference for offline viewing, and step through the sources (including patches and updates) during debugging; see instructions.

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>. Collections that implement IEnumerable<T> can be enumerated by using the foreach statement. For the non-generic version of this interface, see System.Collections.IEnumerable.

For the non-generic version of this interface, see System.Collections.IEnumerable.

IEnumerable<T> contains a single method that you must implement when implementing this interface; GetEnumerator, which returns an IEnumerator<T> object. The returned IEnumerator<T> provides the ability to iterate through the collection by exposing a Current property.

Methods

Get​Enumerator()

Returns an enumerator that iterates through the collection.

Extension Methods

ToImmutableArray<TSource>(IEnumerable<TSource>)

Creates an immutable array from the specified collection.

ToImmutableDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

Constructs an immutable dictionary from an existing collection of elements, applying a transformation function to the source keys.

ToImmutableDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)

Constructs an immutable dictionary based on some transformation of a sequence.

ToImmutableDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>)

Enumerates a sequence of key/value pairs and produces an immutable dictionary of its contents.

ToImmutableDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>, IEqualityComparer<TKey>)

Enumerates a sequence of key/value pairs and produces an immutable dictionary of its contents by using the specified key comparer.

ToImmutableDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>, IEqualityComparer<TKey>, IEqualityComparer<TValue>)

Enumerates a sequence of key/value pairs and produces an immutable dictionary of its contents by using the specified key and value comparers.

ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>)

Enumerates and transforms a sequence, and produces an immutable dictionary of its contents.

ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IEqualityComparer<TKey>)

Enumerates and transforms a sequence, and produces an immutable dictionary of its contents by using the specified key comparer.

ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IEqualityComparer<TKey>, IEqualityComparer<TValue>)

Enumerates and transforms a sequence, and produces an immutable dictionary of its contents by using the specified key and value comparers.

ToImmutableHashSet<TSource>(IEnumerable<TSource>)

Enumerates a sequence and produces an immutable hash set of its contents.

ToImmutableHashSet<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)

Enumerates a sequence, produces an immutable hash set of its contents, and uses the specified equality comparer for the set type.

ToImmutableList<TSource>(IEnumerable<TSource>)

Enumerates a sequence and produces an immutable list of its contents.

ToImmutableSortedDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>)

Enumerates a sequence of key/value pairs and produces an immutable sorted dictionary of its contents.

ToImmutableSortedDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>, IComparer<TKey>)

Enumerates a sequence of key/value pairs and produces an immutable dictionary of its contents by using the specified key comparer.

ToImmutableSortedDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>, IComparer<TKey>, IEqualityComparer<TValue>)

Enumerates a sequence of key/value pairs and produces an immutable sorted dictionary of its contents by using the specified key and value comparers.

ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>)

Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents.

ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IComparer<TKey>)

Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents by using the specified key comparer.

ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IComparer<TKey>, IEqualityComparer<TValue>)

Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents by using the specified key and value comparers.

ToImmutableSortedSet<TSource>(IEnumerable<TSource>)

Enumerates a sequence and produces an immutable sorted set of its contents.

ToImmutableSortedSet<TSource>(IEnumerable<TSource>, IComparer<TSource>)

Enumerates a sequence, produces an immutable sorted set of its contents, and uses the specified comparer.

CopyToDataTable<T>(IEnumerable<T>)

Returns 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)

Copies 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)

Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.

Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>)

Applies an accumulator function over a sequence.

Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>)

Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value.

Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>)

Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value.

All<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Determines whether all elements of a sequence satisfy a condition.

Any<TSource>(IEnumerable<TSource>)

Determines whether a sequence contains any elements.

Any<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Determines whether any element of a sequence satisfies a condition.

Append<TSource>(IEnumerable<TSource>, TSource)
AsEnumerable<TSource>(IEnumerable<TSource>)

Returns the input typed as IEnumerable<T>.

Average(IEnumerable<Decimal>)

Computes the average of a sequence of Decimal values.

Average(IEnumerable<Double>)

Computes the average of a sequence of Double values.

Average(IEnumerable<Int32>)

Computes the average of a sequence of Int32 values.

Average(IEnumerable<Int64>)

Computes the average of a sequence of Int64 values.

Average(IEnumerable<Nullable<Decimal>>)

Computes the average of a sequence of nullable Decimal values.

Average(IEnumerable<Nullable<Double>>)

Computes the average of a sequence of nullable Double values.

Average(IEnumerable<Nullable<Int32>>)

Computes the average of a sequence of nullable Int32 values.

Average(IEnumerable<Nullable<Int64>>)

Computes the average of a sequence of nullable Int64 values.

Average(IEnumerable<Nullable<Single>>)

Computes the average of a sequence of nullable Single values.

Average(IEnumerable<Single>)

Computes the average of a sequence of Single values.

Average<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)

Computes the average of a sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence.

Average<TSource>(IEnumerable<TSource>, Func<TSource,Double>)

Computes the average of a sequence of Double values that are obtained by invoking a transform function on each element of the input sequence.

Average<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)

Computes the average of a sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence.

Average<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)

Computes the average of a sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence.

Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)

Computes the average of a sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence.

Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)

Computes the average of a sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence.

Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)

Computes the average of a sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence.

Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)

Computes the average of a sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence.

Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)

Computes the average of a sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence.

Average<TSource>(IEnumerable<TSource>, Func<TSource,Single>)

Computes the average of a sequence of Single values that are obtained by invoking a transform function on each element of the input sequence.

Cast<TResult>(IEnumerable)

Casts the elements of an IEnumerable to the specified type.

Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)

Concatenates two sequences.

Contains<TSource>(IEnumerable<TSource>, TSource)

Determines whether a sequence contains a specified element by using the default equality comparer.

Contains<TSource>(IEnumerable<TSource>, TSource, IEqualityComparer<TSource>)

Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>.

Count<TSource>(IEnumerable<TSource>)

Returns the number of elements in a sequence.

Count<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Returns a number that represents how many elements in the specified sequence satisfy a condition.

DefaultIfEmpty<TSource>(IEnumerable<TSource>)

Returns the elements of the specified sequence or the type parameter's default value in a singleton collection if the sequence is empty.

DefaultIfEmpty<TSource>(IEnumerable<TSource>, TSource)

Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty.

Distinct<TSource>(IEnumerable<TSource>)

Returns distinct elements from a sequence by using the default equality comparer to compare values.

Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)

Returns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values.

ElementAt<TSource>(IEnumerable<TSource>, Int32)

Returns the element at a specified index in a sequence.

ElementAtOrDefault<TSource>(IEnumerable<TSource>, Int32)

Returns the element at a specified index in a sequence or a default value if the index is out of range.

Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)

Produces the set difference of two sequences by using the default equality comparer to compare values.

Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)

Produces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values.

First<TSource>(IEnumerable<TSource>)

Returns the first element of a sequence.

First<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Returns the first element in a sequence that satisfies a specified condition.

FirstOrDefault<TSource>(IEnumerable<TSource>)

Returns the first element of a sequence, or a default value if the sequence contains no elements.

FirstOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.

GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

Groups the elements of a sequence according to a specified key selector function.

GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)

Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer.

GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)

Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function.

GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)

Groups the elements of a sequence according to a key selector function. The keys are compared by using a comparer and each group's elements are projected by using a specified function.

GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>)

Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.

GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>)

Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The keys are compared by using a specified comparer.

GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>)

Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The elements of each group are projected by using a specified function.

GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>)

Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function.

GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>,TResult>)

Correlates the elements of two sequences based on equality of keys and groups the results. The default equality comparer is used to compare keys.

GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>,TResult>, IEqualityComparer<TKey>)

Correlates the elements of two sequences based on key equality and groups the results. A specified IEqualityComparer<T> is used to compare keys.

Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)

Produces the set intersection of two sequences by using the default equality comparer to compare values.

Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)

Produces the set intersection of two sequences by using the specified IEqualityComparer<T> to compare values.

Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>)

Correlates the elements of two sequences based on matching keys. The default equality comparer is used to compare keys.

Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>)

Correlates the elements of two sequences based on matching keys. A specified IEqualityComparer<T> is used to compare keys.

Last<TSource>(IEnumerable<TSource>)

Returns the last element of a sequence.

Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Returns the last element of a sequence that satisfies a specified condition.

LastOrDefault<TSource>(IEnumerable<TSource>)

Returns the last element of a sequence, or a default value if the sequence contains no elements.

LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Returns the last element of a sequence that satisfies a condition or a default value if no such element is found.

LongCount<TSource>(IEnumerable<TSource>)

Returns an Int64 that represents the total number of elements in a sequence.

LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Returns an Int64 that represents how many elements in a sequence satisfy a condition.

Max(IEnumerable<Decimal>)

Returns the maximum value in a sequence of Decimal values.

Max(IEnumerable<Double>)

Returns the maximum value in a sequence of Double values.

Max(IEnumerable<Int32>)

Returns the maximum value in a sequence of Int32 values.

Max(IEnumerable<Int64>)

Returns the maximum value in a sequence of Int64 values.

Max(IEnumerable<Nullable<Decimal>>)

Returns the maximum value in a sequence of nullable Decimal values.

Max(IEnumerable<Nullable<Double>>)

Returns the maximum value in a sequence of nullable Double values.

Max(IEnumerable<Nullable<Int32>>)

Returns the maximum value in a sequence of nullable Int32 values.

Max(IEnumerable<Nullable<Int64>>)

Returns the maximum value in a sequence of nullable Int64 values.

Max(IEnumerable<Nullable<Single>>)

Returns the maximum value in a sequence of nullable Single values.

Max(IEnumerable<Single>)

Returns the maximum value in a sequence of Single values.

Max<TSource>(IEnumerable<TSource>)

Returns the maximum value in a generic sequence.

Max<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)

Invokes a transform function on each element of a sequence and returns the maximum Decimal value.

Max<TSource>(IEnumerable<TSource>, Func<TSource,Double>)

Invokes a transform function on each element of a sequence and returns the maximum Double value.

Max<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)

Invokes a transform function on each element of a sequence and returns the maximum Int32 value.

Max<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)

Invokes a transform function on each element of a sequence and returns the maximum Int64 value.

Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)

Invokes a transform function on each element of a sequence and returns the maximum nullable Decimal value.

Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)

Invokes a transform function on each element of a sequence and returns the maximum nullable Double value.

Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)

Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value.

Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)

Invokes a transform function on each element of a sequence and returns the maximum nullable Int64 value.

Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)

Invokes a transform function on each element of a sequence and returns the maximum nullable Single value.

Max<TSource>(IEnumerable<TSource>, Func<TSource,Single>)

Invokes a transform function on each element of a sequence and returns the maximum Single value.

Max<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)

Invokes a transform function on each element of a generic sequence and returns the maximum resulting value.

Min(IEnumerable<Decimal>)

Returns the minimum value in a sequence of Decimal values.

Min(IEnumerable<Double>)

Returns the minimum value in a sequence of Double values.

Min(IEnumerable<Int32>)

Returns the minimum value in a sequence of Int32 values.

Min(IEnumerable<Int64>)

Returns the minimum value in a sequence of Int64 values.

Min(IEnumerable<Nullable<Decimal>>)

Returns the minimum value in a sequence of nullable Decimal values.

Min(IEnumerable<Nullable<Double>>)

Returns the minimum value in a sequence of nullable Double values.

Min(IEnumerable<Nullable<Int32>>)

Returns the minimum value in a sequence of nullable Int32 values.

Min(IEnumerable<Nullable<Int64>>)

Returns the minimum value in a sequence of nullable Int64 values.

Min(IEnumerable<Nullable<Single>>)

Returns the minimum value in a sequence of nullable Single values.

Min(IEnumerable<Single>)

Returns the minimum value in a sequence of Single values.

Min<TSource>(IEnumerable<TSource>)

Returns the minimum value in a generic sequence.

Min<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)

Invokes a transform function on each element of a sequence and returns the minimum Decimal value.

Min<TSource>(IEnumerable<TSource>, Func<TSource,Double>)

Invokes a transform function on each element of a sequence and returns the minimum Double value.

Min<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)

Invokes a transform function on each element of a sequence and returns the minimum Int32 value.

Min<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)

Invokes a transform function on each element of a sequence and returns the minimum Int64 value.

Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)

Invokes a transform function on each element of a sequence and returns the minimum nullable Decimal value.

Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)

Invokes a transform function on each element of a sequence and returns the minimum nullable Double value.

Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)

Invokes a transform function on each element of a sequence and returns the minimum nullable Int32 value.

Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)

Invokes a transform function on each element of a sequence and returns the minimum nullable Int64 value.

Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)

Invokes a transform function on each element of a sequence and returns the minimum nullable Single value.

Min<TSource>(IEnumerable<TSource>, Func<TSource,Single>)

Invokes a transform function on each element of a sequence and returns the minimum Single value.

Min<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)

Invokes a transform function on each element of a generic sequence and returns the minimum resulting value.

OfType<TResult>(IEnumerable)

Filters the elements of an IEnumerable based on a specified type.

OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

Sorts the elements of a sequence in ascending order according to a key.

OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)

Sorts the elements of a sequence in ascending order by using a specified comparer.

OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

Sorts the elements of a sequence in descending order according to a key.

OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)

Sorts the elements of a sequence in descending order by using a specified comparer.

Prepend<TSource>(IEnumerable<TSource>, TSource)
Reverse<TSource>(IEnumerable<TSource>)

Inverts the order of the elements in a sequence.

Select<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)

Projects each element of a sequence into a new form.

Select<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,TResult>)

Projects each element of a sequence into a new form by incorporating the element's index.

SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>)

Projects each element of a sequence to an IEnumerable<T> and flattens the resulting sequences into one sequence.

SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>)

Projects each element of a sequence to an IEnumerable<T>, and flattens the resulting sequences into one sequence. The index of each source element is used in the projected form of that element.

SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)

Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein.

SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)

Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. The index of each source element is used in the intermediate projected form of that element.

SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)

Determines whether two sequences are equal by comparing the elements by using the default equality comparer for their type.

SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)

Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer<T>.

Single<TSource>(IEnumerable<TSource>)

Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence.

Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists.

SingleOrDefault<TSource>(IEnumerable<TSource>)

Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.

SingleOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.

Skip<TSource>(IEnumerable<TSource>, Int32)

Bypasses a specified number of elements in a sequence and then returns the remaining elements.

SkipLast<TSource>(IEnumerable<TSource>, Int32)
SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.

SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)

Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. The element's index is used in the logic of the predicate function.

Sum(IEnumerable<Decimal>)

Computes the sum of a sequence of Decimal values.

Sum(IEnumerable<Double>)

Computes the sum of a sequence of Double values.

Sum(IEnumerable<Int32>)

Computes the sum of a sequence of Int32 values.

Sum(IEnumerable<Int64>)

Computes the sum of a sequence of Int64 values.

Sum(IEnumerable<Nullable<Decimal>>)

Computes the sum of a sequence of nullable Decimal values.

Sum(IEnumerable<Nullable<Double>>)

Computes the sum of a sequence of nullable Double values.

Sum(IEnumerable<Nullable<Int32>>)

Computes the sum of a sequence of nullable Int32 values.

Sum(IEnumerable<Nullable<Int64>>)

Computes the sum of a sequence of nullable Int64 values.

Sum(IEnumerable<Nullable<Single>>)

Computes the sum of a sequence of nullable Single values.

Sum(IEnumerable<Single>)

Computes the sum of a sequence of Single values.

Sum<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)

Computes the sum of the sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence.

Sum<TSource>(IEnumerable<TSource>, Func<TSource,Double>)

Computes the sum of the sequence of Double values that are obtained by invoking a transform function on each element of the input sequence.

Sum<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)

Computes the sum of the sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence.

Sum<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)

Computes the sum of the sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence.

Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)

Computes the sum of the sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence.

Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)

Computes the sum of the sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence.

Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)

Computes the sum of the sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence.

Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)

Computes the sum of the sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence.

Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)

Computes the sum of the sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence.

Sum<TSource>(IEnumerable<TSource>, Func<TSource,Single>)

Computes the sum of the sequence of Single values that are obtained by invoking a transform function on each element of the input sequence.

Take<TSource>(IEnumerable<TSource>, Int32)

Returns a specified number of contiguous elements from the start of a sequence.

TakeLast<TSource>(IEnumerable<TSource>, Int32)
TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Returns elements from a sequence as long as a specified condition is true.

TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)

Returns elements from a sequence as long as a specified condition is true. The element's index is used in the logic of the predicate function.

ToArray<TSource>(IEnumerable<TSource>)

Creates an array from a IEnumerable<T>.

ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function.

ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)

Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function and key comparer.

ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)

Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to specified key selector and element selector functions.

ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)

Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function, a comparer, and an element selector function.

ToHashSet<TSource>(IEnumerable<TSource>)
ToHashSet<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)
ToList<TSource>(IEnumerable<TSource>)

Creates a List<T> from an IEnumerable<T>.

ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function.

ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)

Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function and key comparer.

ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)

Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to specified key selector and element selector functions.

ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)

Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function, a comparer and an element selector function.

Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)

Produces the set union of two sequences by using the default equality comparer.

Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)

Produces the set union of two sequences by using a specified IEqualityComparer<T>.

Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Filters a sequence of values based on a predicate.

Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)

Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function.

Zip<TFirst,TSecond,TResult>(IEnumerable<TFirst>, IEnumerable<TSecond>, Func<TFirst,TSecond,TResult>)

Applies a specified function to the corresponding elements of two sequences, producing a sequence of the results.

AsParallel(IEnumerable)

Enables parallelization of a query.

AsParallel<TSource>(IEnumerable<TSource>)

Enables parallelization of a query.

AsQueryable(IEnumerable)

Converts an IEnumerable to an IQueryable.

AsQueryable<TElement>(IEnumerable<TElement>)

Converts a generic IEnumerable<T> to a generic IQueryable<T>.

Ancestors<T>(IEnumerable<T>)

Returns a collection of elements that contains the ancestors of every node in the source collection.

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

Returns a filtered collection of elements that contains the ancestors of every node in the source collection. Only elements that have a matching XName are included in the collection.

AncestorsAndSelf(IEnumerable<XElement>)

Returns a collection of elements that contains every element in the source collection, and the ancestors of every element in the source collection.

AncestorsAndSelf(IEnumerable<XElement>, XName)

Returns a filtered collection of elements that contains every element in the source collection, and the ancestors of every element in the source collection. Only elements that have a matching XName are included in the collection.

Attributes(IEnumerable<XElement>)

Returns a collection of the attributes of every element in the source collection.

Attributes(IEnumerable<XElement>, XName)

Returns a filtered collection of the attributes of every element in the source collection. Only elements that have a matching XName are included in the collection.

DescendantNodes<T>(IEnumerable<T>)

Returns a collection of the descendant nodes of every document and element in the source collection.

DescendantNodesAndSelf(IEnumerable<XElement>)

Returns a collection of nodes that contains every element in the source collection, and the descendant nodes of every element in the source collection.

Descendants<T>(IEnumerable<T>)

Returns a collection of elements that contains the descendant elements of every element and document in the source collection.

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

Returns a filtered collection of elements that contains the descendant elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.

DescendantsAndSelf(IEnumerable<XElement>)

Returns a collection of elements that contains every element in the source collection, and the descendent elements of every element in the source collection.

DescendantsAndSelf(IEnumerable<XElement>, XName)

Returns a filtered collection of elements that contains every element in the source collection, and the descendents of every element in the source collection. Only elements that have a matching XName are included in the collection.

Elements<T>(IEnumerable<T>)

Returns a collection of the child elements of every element and document in the source collection.

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

Returns a filtered collection of the child elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.

InDocumentOrder<T>(IEnumerable<T>)

Returns a collection of nodes that contains all nodes in the source collection, sorted in document order.

Nodes<T>(IEnumerable<T>)

Returns a collection of the child nodes of every document and element in the source collection.

Remove(IEnumerable<XAttribute>)

Removes every attribute in the source collection from its parent element.

Remove<T>(IEnumerable<T>)

Removes every node in the source collection from its parent node.