ParallelEnumerable.GroupBy<TSource, TKey, TElement> Method (ParallelQuery<TSource>, Func<TSource, TKey>, Func<TSource, TElement>, IEqualityComparer<TKey>)
Groups in parallel 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.
Assembly: System.Core (in System.Core.dll)
public static ParallelQuery<IGrouping<TKey, TElement>> GroupBy<TSource, TKey, TElement>( this ParallelQuery<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer )
Parameters
- source
-
Type:
System.Linq.ParallelQuery<TSource>
An OrderedParallelQuery{TSource}that contains elements to sort.
- keySelector
-
Type:
System.Func<TSource, TKey>
A function to extract a key from an element.
- elementSelector
-
Type:
System.Func<TSource, TElement>
A function to map each source element to an element in an IGrouping.
- comparer
-
Type:
System.Collections.Generic.IEqualityComparer<TKey>
An IComparer{TSource} to compare keys.
Return Value
Type: System.Linq.ParallelQuery<IGrouping<TKey, TElement>>A sequence of groups that are sorted descending according to TKey.
Type Parameters
- TSource
The type of elements of source.
- TKey
The type of the key returned by keySelector.
- TElement
The type of the elements in the IGrouping
| 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. |
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone
Available since 8.1