QueryableExtensions.FirstAsync Method

 

Asynchronously returns the first element of a sequence.

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

NameDescription
System_CAPS_pubmethodSystem_CAPS_staticFirstAsync<TSource>(IQueryable<TSource>)

Asynchronously returns the first element of a sequence.

System_CAPS_pubmethodSystem_CAPS_staticFirstAsync<TSource>(IQueryable<TSource>, CancellationToken)

Asynchronously returns the first element of a sequence.

System_CAPS_pubmethodSystem_CAPS_staticFirstAsync<TSource>(IQueryable<TSource>, Expression<Func<TSource, Boolean>>)

Asynchronously returns the first element of a sequence that satisfies a specified condition.

System_CAPS_pubmethodSystem_CAPS_staticFirstAsync<TSource>(IQueryable<TSource>, Expression<Func<TSource, Boolean>>, CancellationToken)

Asynchronously returns the first element of a sequence that satisfies a specified condition.


QueryableExtensions.FirstAsync<TSource> Method (IQueryable<TSource>)

Asynchronously returns the first element of a sequence.

public static Task<TSource> FirstAsync<TSource>(
	this IQueryable<TSource> source
)

Parameters

source
Type: System.Linq.IQueryable<TSource>

An IQueryable<T> to return the first element of.

Return Value

Type: System.Threading.Tasks.Task<TSource>

A task that represents the asynchronous operation. The task result contains the first element in source.

Type Parameters

TSource

The type of the elements of source.

Exception Condition
ArgumentNullException

source is null.

InvalidOperationException

source does not implement IDbAsyncQueryProvider.

InvalidOperationException

The source sequence is empty.

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.


QueryableExtensions.FirstAsync<TSource> Method (IQueryable<TSource>, CancellationToken)

Asynchronously returns the first element of a sequence.

public static Task<TSource> FirstAsync<TSource>(
	this IQueryable<TSource> source,
	CancellationToken cancellationToken
)

Parameters

source
Type: System.Linq.IQueryable<TSource>

An IQueryable<T> to return the first element of.

cancellationToken
Type: System.Threading.CancellationToken

A CancellationToken to observe while waiting for the task to complete.

Return Value

Type: System.Threading.Tasks.Task<TSource>

A task that represents the asynchronous operation. The task result contains the first element in source.

Type Parameters

TSource

The type of the elements of source.

Exception Condition
ArgumentNullException

source is null .

InvalidOperationException

source does not implement IDbAsyncQueryProvider .

InvalidOperationException

The source sequence is empty.

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.


QueryableExtensions.FirstAsync<TSource> Method (IQueryable<TSource>, Expression<Func<TSource, Boolean>>)

Asynchronously returns the first element of a sequence that satisfies a specified condition.

[SuppressMessageAttribute("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures")]
public static Task<TSource> FirstAsync<TSource>(
	this IQueryable<TSource> source,
	Expression<Func<TSource, bool>> predicate
)

Parameters

source
Type: System.Linq.IQueryable<TSource>

An IQueryable<T> to return the first element of.

predicate
Type: System.Linq.Expressions.Expression<Func<TSource, Boolean>>

A function to test each element for a condition.

Return Value

Type: System.Threading.Tasks.Task<TSource>

A task that represents the asynchronous operation. The task result contains the first element in source that passes the test in predicate.

Type Parameters

TSource

The type of the elements of source.

Exception Condition
ArgumentNullException

source or predicate is null .

InvalidOperationException

source does not implement IDbAsyncQueryProvider .

InvalidOperationException

No element satisfies the condition in predicate .

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.


QueryableExtensions.FirstAsync<TSource> Method (IQueryable<TSource>, Expression<Func<TSource, Boolean>>, CancellationToken)

Asynchronously returns the first element of a sequence that satisfies a specified condition.

[SuppressMessageAttribute("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters")]
[SuppressMessageAttribute("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures")]
public static Task<TSource> FirstAsync<TSource>(
	this IQueryable<TSource> source,
	Expression<Func<TSource, bool>> predicate,
	CancellationToken cancellationToken
)

Parameters

source
Type: System.Linq.IQueryable<TSource>

An IQueryable<T> to return the first element of.

predicate
Type: System.Linq.Expressions.Expression<Func<TSource, Boolean>>

A function to test each element for a condition.

cancellationToken
Type: System.Threading.CancellationToken

A CancellationToken to observe while waiting for the task to complete.

Return Value

Type: System.Threading.Tasks.Task<TSource>

A task that represents the asynchronous operation. The task result contains the first element in source that passes the test in predicate.

Type Parameters

TSource

The type of the elements of source.

Exception Condition
ArgumentNullException

source or predicate is null .

InvalidOperationException

source does not implement IDbAsyncQueryProvider .

InvalidOperationException

No element satisfies the condition in predicate .

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.