ParallelEnumerable.GroupBy<'TSource, 'TKey, 'TElement, 'TResult> Method (ParallelQuery<'TSource>, Func<'TSource, 'TKey>, Func<'TSource, 'TElement>, Func<'TKey, IEnumerable<'TElement>, 'TResult>, IEqualityComparer<'TKey>)

.NET Framework (current version)
 
System_CAPS_noteNote

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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.

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

static member GroupBy<'TSource, 'TKey, 'TElement, 'TResult> : 
        source:ParallelQuery<'TSource> *
        keySelector:Func<'TSource, 'TKey> *
        elementSelector:Func<'TSource, 'TElement> *
        resultSelector:Func<'TKey, IEnumerable<'TElement>, 'TResult> *
        comparer:IEqualityComparer<'TKey> -> ParallelQuery<'TResult>

Parameters

source
Type: System.Linq.ParallelQuery<'TSource>

A sequence whose elements to group.

keySelector
Type: System.Func<'TSource, 'TKey>

A function to extract the key for each element.

elementSelector
Type: System.Func<'TSource, 'TElement>

A function to map each source element to an element in an IGrouping{Key, TElement}.

resultSelector
Type: System.Func<'TKey, IEnumerable<'TElement>, 'TResult>

A function to create a result value from each group.

comparer
Type: System.Collections.Generic.IEqualityComparer<'TKey>

An IEqualityComparer<'T> to compare keys.

Return Value

Type: System.Linq.ParallelQuery<'TResult>

A sequence of elements of type TResult where each element represents a projection over a group and its key.

Type Parameters

TSource

The type of the elements of source.

TKey

The type of the key returned by keySelector.

TElement

The type of the elements in each IGrouping{TKey, TElement}.

TResult

The type of the result value returned by resultSelector.

Exception Condition
OperationCanceledException

The query was canceled with the token passed in through WithCancellation.

ArgumentNullException

source or action is a null reference (Nothing in Visual Basic).

AggregateException

One or more exceptions occurred during the evaluation of the query.

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone
Available since 8.1
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