AsyncEnumerable.SingleOrDefaultAsync Method
Definition
Important
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Overloads
| SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, CancellationToken) |
Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence. |
| SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,Boolean>, CancellationToken) |
Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition. |
| SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,CancellationToken,ValueTask<Boolean>>, CancellationToken) |
Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition. |
| SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, TSource, CancellationToken) |
Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence. |
| SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,Boolean>, TSource, CancellationToken) |
Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition. |
| SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,CancellationToken,ValueTask<Boolean>>, TSource, CancellationToken) |
Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition. |
SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, CancellationToken)
- Source:
- SingleAsync.cs
Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.
public static System.Threading.Tasks.ValueTask<TSource?> SingleOrDefaultAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, System.Threading.CancellationToken cancellationToken = default);static member SingleOrDefaultAsync : System.Collections.Generic.IAsyncEnumerable<'Source> * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<'Source><Extension()>
Public Function SingleOrDefaultAsync(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>
An IAsyncEnumerable<T> to return the single element of.
- cancellationToken
- CancellationToken
The CancellationToken to monitor for cancellation requests. The default is None.
Returns
The single element of the input sequence, or the default value of TSource
if the sequence contains no elements.
Exceptions
source is null.
The source sequence contains more than one element. (via the returned task).
Applies to
SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,Boolean>, CancellationToken)
- Source:
- SingleAsync.cs
Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.
public static System.Threading.Tasks.ValueTask<TSource?> SingleOrDefaultAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, Func<TSource,bool> predicate, System.Threading.CancellationToken cancellationToken = default);static member SingleOrDefaultAsync : System.Collections.Generic.IAsyncEnumerable<'Source> * Func<'Source, bool> * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<'Source><Extension()>
Public Function SingleOrDefaultAsync(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 the single element of.
- cancellationToken
- CancellationToken
The CancellationToken to monitor for cancellation requests. The default is None.
Returns
The single element of the input sequence that satisfies the condition, or the default value of
TSource if no such element is found.
Exceptions
predicate is null.
The input sequence contains more than one element.
Applies to
SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,CancellationToken,ValueTask<Boolean>>, CancellationToken)
- Source:
- SingleAsync.cs
Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.
public static System.Threading.Tasks.ValueTask<TSource?> SingleOrDefaultAsync<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 SingleOrDefaultAsync : 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 SingleOrDefaultAsync(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 the single element of.
- predicate
- Func<TSource,CancellationToken,ValueTask<Boolean>>
A function to test an element for a condition.
- cancellationToken
- CancellationToken
The CancellationToken to monitor for cancellation requests. The default is None.
Returns
The single element of the input sequence that satisfies the condition, or the default value of
TSource if no such element is found.
Exceptions
predicate is null.
The input sequence contains more than one element.
Applies to
SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, TSource, CancellationToken)
- Source:
- SingleAsync.cs
Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.
public static System.Threading.Tasks.ValueTask<TSource> SingleOrDefaultAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, TSource defaultValue, System.Threading.CancellationToken cancellationToken = default);static member SingleOrDefaultAsync : System.Collections.Generic.IAsyncEnumerable<'Source> * 'Source * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<'Source><Extension()>
Public Function SingleOrDefaultAsync(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>
An IAsyncEnumerable<T> to return the single 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
The single element of the input sequence, or defaultValue if the sequence contains no elements.
Exceptions
source is null.
The input sequence contains more than one element.
Applies to
SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,Boolean>, TSource, CancellationToken)
- Source:
- SingleAsync.cs
Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.
public static System.Threading.Tasks.ValueTask<TSource> SingleOrDefaultAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, Func<TSource,bool> predicate, TSource defaultValue, System.Threading.CancellationToken cancellationToken = default);static member SingleOrDefaultAsync : System.Collections.Generic.IAsyncEnumerable<'Source> * Func<'Source, bool> * 'Source * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<'Source><Extension()>
Public Function SingleOrDefaultAsync(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 a single 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
The single element of the input sequence that satisfies the condition, or defaultValue if no such element is found.
Exceptions
predicate is null.
More than one element satisfies the condition in predicate.
Applies to
SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource,CancellationToken,ValueTask<Boolean>>, TSource, CancellationToken)
- Source:
- SingleAsync.cs
Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.
public static System.Threading.Tasks.ValueTask<TSource> SingleOrDefaultAsync<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 SingleOrDefaultAsync : 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 SingleOrDefaultAsync(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 a single element from.
- predicate
- Func<TSource,CancellationToken,ValueTask<Boolean>>
A function to test an 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
The single element of the input sequence that satisfies the condition, or defaultValue if no such element is found.
Exceptions
predicate is null.
More than one element satisfies the condition in predicate.
