ParallelEnumerable.GroupBy(Of TSource, TKey, TElement, TResult) Method (ParallelQuery(Of TSource), Func(Of TSource, TKey), Func(Of TSource, TElement), Func(Of TKey, IEnumerable(Of TElement), TResult))
Groups in parallel 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.
Assembly: System.Core (in System.Core.dll)
<ExtensionAttribute> Public Shared Function GroupBy(Of TSource, TKey, TElement, TResult) ( source As ParallelQuery(Of TSource), keySelector As Func(Of TSource, TKey), elementSelector As Func(Of TSource, TElement), resultSelector As Func(Of TKey, IEnumerable(Of TElement), TResult) ) As ParallelQuery(Of TResult)
Parameters
- source
-
Type:
System.Linq.ParallelQuery(Of TSource)
A sequence whose elements to group.
- keySelector
-
Type:
System.Func(Of TSource, TKey)
A function to extract the key for each element.
- elementSelector
-
Type:
System.Func(Of TSource, TElement)
A function to map each source element to an element in an IGrouping<TKey, TElement>.
- resultSelector
-
Type:
System.Func(Of TKey, IEnumerable(Of TElement), TResult)
A function to create a result value from each group.
Return Value
Type: System.Linq.ParallelQuery(Of 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. |
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone
Available since 8.1