QueryableExtensions.ContainsAsync<TSource> Method (IQueryable<TSource>, TSource, CancellationToken)
[This page is specific to the Entity Framework version 6. The latest version is available as the 'Entity Framework' NuGet package. For more information about Entity Framework, see msdn.com/data/ef.]
Asynchronously determines whether a sequence contains a specified element by using the default equality comparer.
Namespace: System.Data.Entity
Assembly: EntityFramework (in EntityFramework.dll)
Syntax
'Declaration
<ExtensionAttribute> _
Public Shared Function ContainsAsync(Of TSource) ( _
source As IQueryable(Of TSource), _
item As TSource, _
cancellationToken As CancellationToken _
) As Task(Of Boolean)
'Usage
Dim source As IQueryable(Of TSource)
Dim item As TSource
Dim cancellationToken As CancellationToken
Dim returnValue As Task(Of Boolean)
returnValue = source.ContainsAsync(item, _
cancellationToken)
public static Task<bool> ContainsAsync<TSource>(
this IQueryable<TSource> source,
TSource item,
CancellationToken cancellationToken
)
[ExtensionAttribute]
public:
generic<typename TSource>
static Task<bool>^ ContainsAsync(
IQueryable<TSource>^ source,
TSource item,
CancellationToken cancellationToken
)
static member ContainsAsync :
source:IQueryable<'TSource> *
item:'TSource *
cancellationToken:CancellationToken -> Task<bool>
JScript does not support generic types and methods.
Type Parameters
- TSource
The type of the elements of source.
Parameters
- source
Type: System.Linq.IQueryable<TSource>
An IQueryable<T> to return the single element of.
- item
Type: TSource
The object to locate in the sequence.
- cancellationToken
Type: System.Threading.CancellationToken
A CancellationToken to observe while waiting for the task to complete.
Return Value
Type: System.Threading.Tasks.Task<Boolean>
A task that represents the asynchronous operation. The task result contains true if the input sequence contains the specified value; otherwise, false.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IQueryable<TSource>. When you use instance method syntax to call this method, omit the first parameter. For more information, see https://msdn.microsoft.com/en-us/library/bb384936(v=vs.113) or https://msdn.microsoft.com/en-us/library/bb383977(v=vs.113).
Exceptions
Exception | Condition |
---|---|
ArgumentNullException | source is null . |
InvalidOperationException | source does not implement IDbAsyncQueryProvider . |
Remarks
Multiple active operations on the same context instance are not supported. Use 'await' to ensure that any asynchronous operations have completed before calling another method on this context.