QueryableExtensions.AverageAsync<TSource> Method (IQueryable<TSource>, Expression<Func<TSource, Nullable<Int64>>>, CancellationToken)

Article
12/10/2014

[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 computes the average of a sequence of nullable Int64 values that is obtained by invoking a projection function on each element of the input sequence.

Namespace: System.Data.Entity
Assembly: EntityFramework (in EntityFramework.dll)

Syntax

'Declaration
<SuppressMessageAttribute("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters")> _
<SuppressMessageAttribute("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures")> _
<ExtensionAttribute> _
Public Shared Function AverageAsync(Of TSource) ( _
    source As IQueryable(Of TSource), _
    selector As Expression(Of Func(Of TSource, Nullable(Of Long))), _
    cancellationToken As CancellationToken _
) As Task(Of Nullable(Of Double))
'Usage
Dim source As IQueryable(Of TSource)
Dim selector As Expression(Of Func(Of TSource, Nullable(Of Long)))
Dim cancellationToken As CancellationToken 
Dim returnValue As Task(Of Nullable(Of Double))

returnValue = source.AverageAsync(selector, _
    cancellationToken)

[SuppressMessageAttribute("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters")]
[SuppressMessageAttribute("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures")]
public static Task<Nullable<double>> AverageAsync<TSource>(
    this IQueryable<TSource> source,
    Expression<Func<TSource, Nullable<long>>> selector,
    CancellationToken cancellationToken
)

[SuppressMessageAttribute(L"Microsoft.Design", L"CA1011:ConsiderPassingBaseTypesAsParameters")]
[SuppressMessageAttribute(L"Microsoft.Design", L"CA1006:DoNotNestGenericTypesInMemberSignatures")]
[ExtensionAttribute]
public:
generic<typename TSource>
static Task<Nullable<double>>^ AverageAsync(
    IQueryable<TSource>^ source, 
    Expression<Func<TSource, Nullable<long long>>^>^ selector, 
    CancellationToken cancellationToken
)

[<SuppressMessageAttribute("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters")>]
[<SuppressMessageAttribute("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures")>]
static member AverageAsync : 
        source:IQueryable<'TSource> * 
        selector:Expression<Func<'TSource, Nullable<int64>>> * 
        cancellationToken:CancellationToken -> Task<Nullable<float>>

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>
A sequence of values to calculate the average of.

selector
Type: System.Linq.Expressions.Expression<Func<TSource, Nullable<Int64>>>
A projection function to apply to each element.

cancellationToken
Type: System.Threading.CancellationToken
A CancellationToken to observe while waiting for the task to complete.

Return Value

Type: System.Threading.Tasks.Task<Nullable<Double>>
A task that represents the asynchronous operation. The task result contains the average of the sequence of values.

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 or selector 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.