ParallelEnumerable.ToLookup<TSource, TKey, TElement> Method (ParallelQuery<TSource>, Func<TSource, TKey>, Func<TSource, TElement>)
Creates an ILookup<TKey, TElement> from a ParallelQuery<TSource> according to specified key selector and element selector functions.
Assembly: System.Core (in System.Core.dll)
public static ILookup<TKey, TElement> ToLookup<TSource, TKey, TElement>( this ParallelQuery<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector )
Parameters
- source
-
Type:
System.Linq.ParallelQuery<TSource>
The sequence to create a ILookup<TKey, TElement> from.
- keySelector
-
Type:
System.Func<TSource, TKey>
A function to extract a key from each element.
- elementSelector
-
Type:
System.Func<TSource, TElement>
A transform function to produce a result element value from each element.
Return Value
Type: System.Linq.ILookup<TKey, TElement>A ILookup<TKey, TElement> that contains values of type TElement selected from the input sequence.
Type Parameters
- TSource
The type of elements of source.
- TKey
The type of the key returned by keySelector.
- TElement
The type of the value returned by elementSelector.
| Exception | Condition |
|---|---|
| OperationCanceledException | The query was canceled with the token passed in through WithCancellation. |
| ArgumentNullException | source or keySelector or elementSelector 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