Creates an ILookup{TKey,TElement} from a ParallelQuery{T} according to
a specified key selector function, a comparer and an element selector function.
Namespace:
System.Linq
Assembly:
System.Threading (in System.Threading.dll)
Syntax
| Visual Basic (Declaration) |
|---|
Public Shared Function ToLookup(Of TSource, TKey, TElement) ( _
source As ParallelQuery(Of TSource), _
keySelector As Func(Of TSource, TKey), _
elementSelector As Func(Of TSource, TElement), _
comparer As IEqualityComparer(Of TKey) _
) As ILookup(Of TKey, TElement) |
| C# |
|---|
public static ILookup<TKey, TElement> ToLookup<TSource, TKey, TElement>(
ParallelQuery<TSource> source,
Func<TSource, TKey> keySelector,
Func<TSource, TElement> elementSelector,
IEqualityComparer<TKey> comparer
)
|
Parameters
- source
- Type: System.Linq..::.ParallelQuery<(Of <(TSource>)>)
The sequence to create a Lookup<(Of <(TKey, TElement>)>) from.
- keySelector
- Type: System..::.Func<(Of <(TSource, TKey>)>)
A function to extract a key from each element.
- elementSelector
- Type: System..::.Func<(Of <(TSource, TElement>)>)
A transform function to produce a result element value from each element.
- comparer
- Type: System.Collections.Generic..::.IEqualityComparer<(Of <(TKey>)>)
An IEqualityComparer<(Of <(T>)>) to compare keys.
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.
Return Value
A Lookup<(Of <(TKey, TElement>)>) that contains values of type TElement selected
from the input sequence.
Exceptions
| Exception | Condition |
|---|
| System..::.ArgumentNullException |
source or keySelector or elementSelector is a null reference (Nothing in Visual Basic).
|
| System..::.AggregateException |
One or more exceptions occurred during the evaluation of the query.
|
| System..::.OperationCanceledException |
The query was canceled.
|
See Also
