AsyncEnumerable.FirstOrDefaultAsync Method
Definition
Important
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Overloads
| FirstOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,Boolean>, TSource, CancellationToken) |
Returns the first element of the sequence that satisfies a condition or a default value if no such element is found. |
| FirstOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, TSource, CancellationToken) |
Returns the first element of a sequence, or a default value if the sequence contains no elements. |
| FirstOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,CancellationToken,ValueTask<Boolean>>, TSource, CancellationToken) |
Returns the first element of the sequence that satisfies a condition or a default value if no such element is found. |
| FirstOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,Boolean>, CancellationToken) |
Returns the first element of the sequence that satisfies a condition or a default value if no such element is found. |
| FirstOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, CancellationToken) |
Returns the first element of a sequence, or the default value of |
| FirstOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,CancellationToken,ValueTask<Boolean>>, CancellationToken) |
Returns the first element of the sequence that satisfies a condition or a default value if no such element is found. |
FirstOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,Boolean>, TSource, CancellationToken)
- Source:
- FirstAsync.cs
Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.
public static System.Threading.Tasks.ValueTask<TSource> FirstOrDefaultAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, Func<TSource,bool> predicate, TSource defaultValue, System.Threading.CancellationToken cancellationToken = default);static member FirstOrDefaultAsync : System.Collections.Generic.IAsyncEnumerable<'Source> * Func<'Source, bool> * 'Source * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<'Source><Extension()>
Public Function FirstOrDefaultAsync(Of TSource) (source As IAsyncEnumerable(Of TSource), predicate As Func(Of TSource, Boolean), defaultValue As TSource, 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.
- defaultValue
- TSource
The default value to return if the sequence is empty.
- cancellationToken
- CancellationToken
The CancellationToken to monitor for cancellation requests. The default is None.
Returns
defaultValue 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.
Exceptions
predicate is null.
Applies to
FirstOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, TSource, CancellationToken)
- Source:
- FirstAsync.cs
Returns the first element of a sequence, or a default value if the sequence contains no elements.
public static System.Threading.Tasks.ValueTask<TSource> FirstOrDefaultAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, TSource defaultValue, System.Threading.CancellationToken cancellationToken = default);static member FirstOrDefaultAsync : System.Collections.Generic.IAsyncEnumerable<'Source> * 'Source * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<'Source><Extension()>
Public Function FirstOrDefaultAsync(Of TSource) (source As IAsyncEnumerable(Of TSource), defaultValue As 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.
- defaultValue
- TSource
The default value to return if the sequence is empty.
- cancellationToken
- CancellationToken
The CancellationToken to monitor for cancellation requests. The default is None.
Returns
defaultValue if source is empty; otherwise, the first element in source.
Exceptions
source is null.
Applies to
FirstOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,CancellationToken,ValueTask<Boolean>>, TSource, CancellationToken)
- Source:
- FirstAsync.cs
Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.
public static System.Threading.Tasks.ValueTask<TSource> FirstOrDefaultAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, Func<TSource,System.Threading.CancellationToken,System.Threading.Tasks.ValueTask<bool>> predicate, TSource defaultValue, System.Threading.CancellationToken cancellationToken = default);static member FirstOrDefaultAsync : System.Collections.Generic.IAsyncEnumerable<'Source> * Func<'Source, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<bool>> * 'Source * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<'Source><Extension()>
Public Function FirstOrDefaultAsync(Of TSource) (source As IAsyncEnumerable(Of TSource), predicate As Func(Of TSource, CancellationToken, ValueTask(Of Boolean)), defaultValue As TSource, 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.
- defaultValue
- TSource
The default value to return if the sequence is empty.
- cancellationToken
- CancellationToken
The CancellationToken to monitor for cancellation requests. The default is None.
Returns
defaultValue 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.
Exceptions
predicate is null.
Applies to
FirstOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,Boolean>, CancellationToken)
- Source:
- FirstAsync.cs
Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.
public static System.Threading.Tasks.ValueTask<TSource?> FirstOrDefaultAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, Func<TSource,bool> predicate, System.Threading.CancellationToken cancellationToken = default);static member FirstOrDefaultAsync : System.Collections.Generic.IAsyncEnumerable<'Source> * Func<'Source, bool> * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<'Source><Extension()>
Public Function FirstOrDefaultAsync(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
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 default value of 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.
Exceptions
predicate is null.
Applies to
FirstOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, CancellationToken)
- Source:
- FirstAsync.cs
Returns the first element of a sequence, or the default value of TSource if the sequence contains no elements.
public static System.Threading.Tasks.ValueTask<TSource?> FirstOrDefaultAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, System.Threading.CancellationToken cancellationToken = default);static member FirstOrDefaultAsync : System.Collections.Generic.IAsyncEnumerable<'Source> * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<'Source><Extension()>
Public Function FirstOrDefaultAsync(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 default value of TSource if source is empty; otherwise, the first element in source.
Exceptions
source is null.
Applies to
FirstOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,CancellationToken,ValueTask<Boolean>>, CancellationToken)
- Source:
- FirstAsync.cs
Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.
public static System.Threading.Tasks.ValueTask<TSource?> FirstOrDefaultAsync<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 FirstOrDefaultAsync : 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 FirstOrDefaultAsync(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
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 default value of 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.
Exceptions
predicate is null.
