AsyncEnumerable.FirstAsync Method
Definition
Important
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Overloads
| FirstAsync<TSource>(IAsyncEnumerable<TSource>, CancellationToken) |
Returns the first element of a sequence. |
| FirstAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,Boolean>, CancellationToken) |
Returns the first element in a sequence that satisfies a specified condition. |
| FirstAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,CancellationToken,ValueTask<Boolean>>, CancellationToken) |
Returns the first element in a sequence that satisfies a specified condition. |
FirstAsync<TSource>(IAsyncEnumerable<TSource>, CancellationToken)
- Source:
- FirstAsync.cs
Returns the first element of a sequence.
public static System.Threading.Tasks.ValueTask<TSource> FirstAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, System.Threading.CancellationToken cancellationToken = default);static member FirstAsync : System.Collections.Generic.IAsyncEnumerable<'Source> * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<'Source><Extension()>
Public Function FirstAsync(Of TSource) (source As IAsyncEnumerable(Of TSource), Optional cancellationToken As CancellationToken = Nothing) As ValueTask(Of TSource)Type Parameters
- TSource
The type of the elements of source.
Parameters
- source
- IAsyncEnumerable<TSource>
The IAsyncEnumerable<T> to return the first element of.
- cancellationToken
- CancellationToken
The CancellationToken to monitor for cancellation requests. The default is None.
Returns
The first element in the specified sequence.
Exceptions
source is null.
The source sequence is empty (via the returned task).
Applies to
FirstAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,Boolean>, CancellationToken)
- Source:
- FirstAsync.cs
Returns the first element in a sequence that satisfies a specified condition.
public static System.Threading.Tasks.ValueTask<TSource> FirstAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, Func<TSource,bool> predicate, System.Threading.CancellationToken cancellationToken = default);static member FirstAsync : System.Collections.Generic.IAsyncEnumerable<'Source> * Func<'Source, bool> * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<'Source><Extension()>
Public Function FirstAsync(Of TSource) (source As IAsyncEnumerable(Of TSource), predicate As Func(Of TSource, Boolean), Optional cancellationToken As CancellationToken = Nothing) As ValueTask(Of TSource)Type Parameters
- TSource
The type of the elements of source.
Parameters
- source
- IAsyncEnumerable<TSource>
An IAsyncEnumerable<T> to return an element from.
- cancellationToken
- CancellationToken
The CancellationToken to monitor for cancellation requests. The default is None.
Returns
The first element in the sequence that passes the test in the specified predicate function.
Exceptions
predicate is null.
The source sequence is empty, or no element in the sequence satisfies the condition in predicate (via the returned task).
Applies to
FirstAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,CancellationToken,ValueTask<Boolean>>, CancellationToken)
- Source:
- FirstAsync.cs
Returns the first element in a sequence that satisfies a specified condition.
public static System.Threading.Tasks.ValueTask<TSource> FirstAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, Func<TSource,System.Threading.CancellationToken,System.Threading.Tasks.ValueTask<bool>> predicate, System.Threading.CancellationToken cancellationToken = default);static member FirstAsync : System.Collections.Generic.IAsyncEnumerable<'Source> * Func<'Source, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<bool>> * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<'Source><Extension()>
Public Function FirstAsync(Of TSource) (source As IAsyncEnumerable(Of TSource), predicate As Func(Of TSource, CancellationToken, ValueTask(Of Boolean)), Optional cancellationToken As CancellationToken = Nothing) As ValueTask(Of TSource)Type Parameters
- TSource
The type of the elements of source.
Parameters
- source
- IAsyncEnumerable<TSource>
An IAsyncEnumerable<T> to return an element from.
- predicate
- Func<TSource,CancellationToken,ValueTask<Boolean>>
A function to test each element for a condition.
- cancellationToken
- CancellationToken
The CancellationToken to monitor for cancellation requests. The default is None.
Returns
The first element in the sequence that passes the test in the specified predicate function.
Exceptions
predicate is null.
The source sequence is empty, or no element in the sequence satisfies the condition in predicate (via the returned task).
