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IEnumerable<T> Interface

Definition

Namespace:
System.Collections.Generic
Assemblies:
mscorlib.dll, System.Runtime.dll
Assemblies:
netstandard.dll, System.Runtime.dll
Assembly:
System.Runtime.dll
Assembly:
mscorlib.dll
Assembly:
netstandard.dll
Source:
IEnumerable.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

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
public interface IEnumerable<out T> : System.Collections.IEnumerable where T : allows ref struct
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

Type Parameters

T

The type of objects to enumerate.

This type parameter is covariant. That is, you can use either the type you specified or any type that is more derived. For more information about covariance and contravariance, seeCovariance and Contravariance in Generics.
Derived
Implements

Examples

The following example demonstrates how to implement theIEnumerable<T> interface and how to use that implementation to create a LINQ query. When you implementIEnumerable<T>, you must also implementIEnumerator<T> or, for C# only, you can use theyield keyword. ImplementingIEnumerator<T> also requiresIDisposable 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{    // Exercise 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(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.IOImports System.CollectionsImports System.Collections.GenericImports System.LinqPublic 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 SubEnd 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 FunctionEnd 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(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 SubEnd Class' This example displays output similar to the following:'       Found: 2'       Memory Used With Iterator =     33kb'       ---'       Found: 2'       Memory Used Without Iterator =  206kb

Remarks

IEnumerable<T> is the base interface for collections in theSystem.Collections.Generic namespace such asList<T>,Dictionary<TKey,TValue>, andStack<T> and other generic collections such asObservableCollection<T> andConcurrentStack<T>. Collections that implementIEnumerable<T> can be enumerated by using theforeach statement.

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

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

Notes to Implementers

To remain compatible with methods that iterate non-generic collections,IEnumerable<T> implementsIEnumerable. This allows a generic collection to be passed to a method that expects anIEnumerable object.

Methods

GetEnumerator()

Returns an enumerator that iterates through the collection.

Extension Methods

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

Creates aFrozenDictionary<TKey,TValue> from anIEnumerable<T> according to specified key selector function.

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

Creates aFrozenDictionary<TKey,TValue> from anIEnumerable<T> according to specified key selector and element selector functions.

ToFrozenSet<T>(IEnumerable<T>, IEqualityComparer<T>)

Creates aFrozenSet<T> with the specified values.

ToImmutableArray<TSource>(IEnumerable<TSource>)

Creates an immutable array from the specified collection.

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

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

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,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.

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>)

Enumerates and transforms a sequence, and produces an immutable dictionary 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.

ToImmutableHashSet<TSource>(IEnumerable<TSource>)

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

ToImmutableList<TSource>(IEnumerable<TSource>)

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

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.

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>)

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

ToImmutableSortedSet<TSource>(IEnumerable<TSource>)

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

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

CopiesDataRow objects to the specifiedDataTable, given an inputIEnumerable<T> object where the generic parameterT isDataRow.

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

CopiesDataRow objects to the specifiedDataTable, given an inputIEnumerable<T> object where the generic parameterT isDataRow.

CopyToDataTable<T>(IEnumerable<T>)

Returns aDataTable that contains copies of theDataRow objects, given an inputIEnumerable<T> object where the generic parameterT isDataRow.

ToAsyncEnumerable<TSource>(IEnumerable<TSource>)

Creates a newIAsyncEnumerable<T> that iterates throughsource.

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.

AggregateBy<TSource,TKey,TAccumulate>(IEnumerable<TSource>, Func<TSource,TKey>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, IEqualityComparer<TKey>)

Applies an accumulator function over a sequence, grouping results by key.

AggregateBy<TSource,TKey,TAccumulate>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,TAccumulate>, Func<TAccumulate,TSource,TAccumulate>, IEqualityComparer<TKey>)

Applies an accumulator function over a sequence, grouping results by key.

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

Determines whether all elements of a sequence satisfy a condition.

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

Determines whether any element of a sequence satisfies a condition.

Any<TSource>(IEnumerable<TSource>)

Determines whether a sequence contains any elements.

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

Appends a value to the end of the sequence.

AsEnumerable<TSource>(IEnumerable<TSource>)

Returns the input typed asIEnumerable<T>.

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

Computes the average of a sequence ofDecimal 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 ofDouble 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 ofInt32 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 ofInt64 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 nullableDecimal 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 nullableDouble 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 nullableInt32 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 nullableInt64 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 nullableSingle 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 ofSingle values that are obtained by invoking a transform function on each element of the input sequence.

Cast<TResult>(IEnumerable)

Casts the elements of anIEnumerable to the specified type.

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

Splits the elements of a sequence into chunks of size at mostsize.

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

Concatenates two sequences.

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

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

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

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

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

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

Count<TSource>(IEnumerable<TSource>)

Returns the number of elements in a sequence.

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

Returns the count of elements in the source sequence grouped by key.

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.

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.

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

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

Distinct<TSource>(IEnumerable<TSource>)

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

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

Returns distinct elements from a sequence according to a specified key selector function and using a specified comparer to compare keys.

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

Returns distinct elements from a sequence according to a specified key selector function.

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

Returns the element at a specified index in a sequence.

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

Returns the element at a specified index in a sequence.

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

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

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>, IEqualityComparer<TSource>)

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

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

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

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

Produces the set difference of two sequences according to a specified key selector function.

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

Produces the set difference of two sequences according to a specified key selector function.

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

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

First<TSource>(IEnumerable<TSource>)

Returns the first element of a sequence.

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

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

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

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

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.

FirstOrDefault<TSource>(IEnumerable<TSource>)

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

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

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

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.

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 specifiedIEqualityComparer<T> 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>)

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

Index<TSource>(IEnumerable<TSource>)

Returns an enumerable that incorporates the element's index into a tuple.

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

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

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

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

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

Produces the set intersection of two sequences according to a specified key selector function.

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

Produces the set intersection of two sequences according to a specified key selector function.

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 specifiedIEqualityComparer<T> is used to compare keys.

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.

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

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

Last<TSource>(IEnumerable<TSource>)

Returns the last element of a sequence.

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

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

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

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

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.

LastOrDefault<TSource>(IEnumerable<TSource>)

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

LeftJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>)
LeftJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>)
LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Returns anInt64 that represents how many elements in a sequence satisfy a condition.

LongCount<TSource>(IEnumerable<TSource>)

Returns anInt64 that represents the total number of elements in a sequence.

Max<TSource>(IEnumerable<TSource>, IComparer<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 maximumDecimal value.

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

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

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

Invokes a transform function on each element of a sequence and returns the maximumInt32 value.

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

Invokes a transform function on each element of a sequence and returns the maximumInt64 value.

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

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

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

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

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

Invokes a transform function on each element of a sequence and returns the maximum nullableInt32 value.

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

Invokes a transform function on each element of a sequence and returns the maximum nullableInt64 value.

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

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

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

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

Max<TSource>(IEnumerable<TSource>)

Returns the maximum value in a generic sequence.

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.

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

Returns the maximum value in a generic sequence according to a specified key selector function and key comparer.

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

Returns the maximum value in a generic sequence according to a specified key selector function.

Min<TSource>(IEnumerable<TSource>, IComparer<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 minimumDecimal value.

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

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

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

Invokes a transform function on each element of a sequence and returns the minimumInt32 value.

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

Invokes a transform function on each element of a sequence and returns the minimumInt64 value.

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

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

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

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

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

Invokes a transform function on each element of a sequence and returns the minimum nullableInt32 value.

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

Invokes a transform function on each element of a sequence and returns the minimum nullableInt64 value.

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

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

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

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

Min<TSource>(IEnumerable<TSource>)

Returns the minimum value in a generic sequence.

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.

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

Returns the minimum value in a generic sequence according to a specified key selector function and key comparer.

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

Returns the minimum value in a generic sequence according to a specified key selector function.

OfType<TResult>(IEnumerable)

Filters the elements of anIEnumerable based on a specified type.

Order<T>(IEnumerable<T>, IComparer<T>)

Sorts the elements of a sequence in ascending order.

Order<T>(IEnumerable<T>)

Sorts the elements of a sequence in ascending order.

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

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

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

Sorts the elements of a sequence in ascending 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.

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

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

OrderDescending<T>(IEnumerable<T>, IComparer<T>)

Sorts the elements of a sequence in descending order.

OrderDescending<T>(IEnumerable<T>)

Sorts the elements of a sequence in descending order.

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

Adds a value to the beginning of the sequence.

Reverse<TSource>(IEnumerable<TSource>)

Inverts the order of the elements in a sequence.

RightJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>)
RightJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>)
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 anIEnumerable<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 anIEnumerable<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 anIEnumerable<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 anIEnumerable<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>, IEqualityComparer<TSource>)

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

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.

Shuffle<TSource>(IEnumerable<TSource>)
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.

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.

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

Returns the only element of a sequence, or a specified 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>, TSource)

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

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.

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.

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)

Returns a new enumerable collection that contains the elements fromsource with the lastcount elements of the source collection omitted.

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

Computes the sum of the sequence ofDecimal 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 ofDouble 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 ofInt32 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 ofInt64 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 nullableDecimal 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 nullableDouble 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 nullableInt32 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 nullableInt64 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 nullableSingle 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 ofSingle 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.

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

Returns a specified range of contiguous elements from a sequence.

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

Returns a new enumerable collection that contains the lastcount elements fromsource.

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 aIEnumerable<T>.

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

Creates aDictionary<TKey,TValue> from anIEnumerable<T> according to a specified key selector function and key comparer.

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

Creates aDictionary<TKey,TValue> from anIEnumerable<T> according to a specified key selector function.

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

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

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

Creates aDictionary<TKey,TValue> from anIEnumerable<T> according to specified key selector and element selector functions.

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

Creates aHashSet<T> from anIEnumerable<T> using thecomparer to compare keys.

ToHashSet<TSource>(IEnumerable<TSource>)

Creates aHashSet<T> from anIEnumerable<T>.

ToList<TSource>(IEnumerable<TSource>)

Creates aList<T> from anIEnumerable<T>.

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

Creates aLookup<TKey,TElement> from anIEnumerable<T> according to a specified key selector function and key comparer.

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

Creates aLookup<TKey,TElement> from anIEnumerable<T> according to a specified key selector function.

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

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

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

Creates aLookup<TKey,TElement> from anIEnumerable<T> according to specified key selector and element selector functions.

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

Attempts to determine the number of elements in a sequence without forcing an enumeration.

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

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

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

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

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

Produces the set union of two sequences according to a specified key selector function.

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

Produces the set union of two sequences according to a specified key selector function.

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>(IEnumerable<TFirst>, IEnumerable<TSecond>)

Produces a sequence of tuples with elements from the two specified sequences.

Zip<TFirst,TSecond,TThird>(IEnumerable<TFirst>, IEnumerable<TSecond>, IEnumerable<TThird>)

Produces a sequence of tuples with elements from the three specified sequences.

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 anIEnumerable to anIQueryable.

AsQueryable<TElement>(IEnumerable<TElement>)

Converts a genericIEnumerable<T> to a genericIQueryable<T>.

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 matchingXName are included in the collection.

Ancestors<T>(IEnumerable<T>)

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

DescendantNodes<T>(IEnumerable<T>)

Returns a collection of the descendant nodes of every document and element 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 matchingXName are included in the collection.

Descendants<T>(IEnumerable<T>)

Returns a collection of elements that contains the descendant 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 matchingXName 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.

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<T>(IEnumerable<T>)

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

Applies to

See also

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