QueryableExtensions.FirstOrDefaultAsync Method

 

Asynchronously returns the first element of a sequence, or a default value if the sequence contains no elements.

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

NameDescription
System_CAPS_pubmethodSystem_CAPS_staticFirstOrDefaultAsync<TSource>(IQueryable<TSource>)

Asynchronously returns the first element of a sequence, or a default value if the sequence contains no elements.

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

Asynchronously returns the first element of a sequence, or a default value if the sequence contains no elements.

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

Asynchronously returns the first element of a sequence that satisfies a specified condition or a default value if no such element is found.

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

Asynchronously returns the first element of a sequence that satisfies a specified condition or a default value if no such element is found.


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

Asynchronously returns the first element of a sequence, or a default value if the sequence contains no elements.

public static Task<TSource> FirstOrDefaultAsync<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 default ( TSource ) if source is empty; otherwise, 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 .

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.FirstOrDefaultAsync<TSource> Method (IQueryable<TSource>, CancellationToken)

Asynchronously returns the first element of a sequence, or a default value if the sequence contains no elements.

public static Task<TSource> FirstOrDefaultAsync<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 default ( TSource ) if source is empty; otherwise, 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 .

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

Asynchronously returns the first element of a sequence that satisfies a specified condition or a default value if no such element is found.

[SuppressMessageAttribute("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures")]
public static Task<TSource> FirstOrDefaultAsync<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 default ( TSource ) if source is empty or if no element passes the test specified by predicate ; otherwise, the first element in source that passes the test specified by 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 .

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

Asynchronously returns the first element of a sequence that satisfies a specified condition or a default value if no such element is found.

[SuppressMessageAttribute("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters")]
[SuppressMessageAttribute("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures")]
public static Task<TSource> FirstOrDefaultAsync<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 default ( TSource ) if source is empty or if no element passes the test specified by predicate ; otherwise, the first element in source that passes the test specified by 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

source has more than one element.

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.