XPQueryExtensions.ToLookupAsync<T, TKey, TElement>(IQueryable<T>, Func<T, TKey>, Func<T, TElement>, IEqualityComparer<TKey>, CancellationToken) Method

Asynchronously enumerates a query and uses a key selector, an element selector and an comparer to construct a Lookup<TKey,TElement>.

Namespace : DevExpress.Xpo

Assembly : DevExpress.Xpo.v25.2.dll

NuGet Package : DevExpress.Xpo

csharp

public static Task<ILookup<TKey, TElement>> ToLookupAsync<T, TKey, TElement>(
    this IQueryable<T> query,
    Func<T, TKey> keySelector,
    Func<T, TElement> elementSelector,
    IEqualityComparer<TKey> equalityComparer,
    CancellationToken cancellationToken = default(CancellationToken)
)

<ExtensionAttribute>
Public Shared Function ToLookupAsync(Of T, TKey, TElement)(
    query As IQueryable(Of T),
    keySelector As Func(Of T, TKey),
    elementSelector As Func(Of T, TElement),
    equalityComparer As IEqualityComparer(Of TKey),
    cancellationToken As CancellationToken = Nothing
) As Task(Of ILookup(Of TKey, TElement))

Parameters

Name	Type	Description
query	IQueryable<T>

An XPQuery<T> to be enumerated.

| | keySelector | Func<T, TKey> |

A function that acquires each persistent object’s key.

| | elementSelector | Func<T, TElement> |

A function that returns a result value for each persistent object.

| | equalityComparer | IEqualityComparer<TKey> |

A function that returns a result value for each persistent object.

Optional Parameters

Name	Type	Default	Description
cancellationToken	CancellationToken	null

A CancellationToken object that delivers a cancellation notice to the running operation.

Type Parameters

Name
T
TKey
TElement

Returns

Type	Description
Task<ILookup<TKey, TElement>>

A Task that returns a Lookup<TKey,TElement>.