Method TrySingle

TrySingle<T, TCardinality>(IAsyncEnumerable<T>, TCardinality, TCardinality, TCardinality, CancellationToken)

Returns a tuple with the cardinality of the sequence and the single element in the sequence if it contains exactly one element. similar to SingleAsync<TSource>(IAsyncEnumerable<TSource>, CancellationToken).

Declaration

public static ValueTask<(TCardinality Cardinality, T? Value)> TrySingle<T, TCardinality>(this IAsyncEnumerable<T> source, TCardinality zero, TCardinality one, TCardinality many, CancellationToken cancellationToken = default)

Parameters

Type	Name	Description
IAsyncEnumerable<T>	source	The source sequence.
TCardinality	zero	The value that is returned in the tuple if the sequence has zero elements.
TCardinality	one	The value that is returned in the tuple if the sequence has a single element only.
TCardinality	many	The value that is returned in the tuple if the sequence has two or more elements.
CancellationToken	cancellationToken	The optional cancellation token to be used for cancelling the sequence at any time.

Returns

Type	Description
ValueTask<(TCardinality Cardinality, T Value)>	A tuple containing the identified TCardinality and either the single value of T in the sequence or its default value.

Type Parameters

Name	Description
T	The type of the elements of source.
TCardinality	The type that expresses cardinality.

Remarks

This operator uses immediate execution, but never consumes more than two elements from the sequence.

Exceptions

Type	Condition
ArgumentNullException	source is null

TrySingle<T, TCardinality, TResult>(IAsyncEnumerable<T>, TCardinality, TCardinality, TCardinality, Func<TCardinality, T?, TResult>, CancellationToken)

Returns a result projected from the the cardinality of the sequence and the single element in the sequence if it contains exactly one element.

Declaration

public static ValueTask<TResult> TrySingle<T, TCardinality, TResult>(this IAsyncEnumerable<T> source, TCardinality zero, TCardinality one, TCardinality many, Func<TCardinality, T?, TResult> resultSelector, CancellationToken cancellationToken = default)

Parameters

Type	Name	Description
IAsyncEnumerable<T>	source	The source sequence.
TCardinality	zero	The value that is passed as the first argument to resultSelector if the sequence has zero elements.
TCardinality	one	The value that is passed as the first argument to resultSelector if the sequence has a single element only.
TCardinality	many	The value that is passed as the first argument to resultSelector if the sequence has two or more elements.
Func<TCardinality, T, TResult>	resultSelector	A function that receives the cardinality and, if the sequence has just one element, the value of that element as argument and projects a resulting value of type TResult.
CancellationToken	cancellationToken	The optional cancellation token to be used for cancelling the sequence at any time.

Returns

Type	Description
ValueTask<TResult>	The value returned by resultSelector.

Type Parameters

Name	Description
T	The type of the elements of source.
TCardinality	The type that expresses cardinality.
TResult	The type of the result value returned by the resultSelector function.

Remarks

This operator uses immediate execution, but never consumes more than two elements from the sequence.

Exceptions

Type	Condition
ArgumentNullException	source is null
ArgumentNullException	resultSelector is null

TrySingle<TSource>(IAsyncEnumerable<TSource>, CancellationToken)

Returns the single element in the sequence if it contains exactly one element. Similar to SingleOrDefaultAsync<TSource>(IAsyncEnumerable<TSource>, CancellationToken).

Declaration

public static ValueTask<TSource?> TrySingle<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken = default)

Parameters

Type	Name	Description
IAsyncEnumerable<TSource>	source	The source sequence.
CancellationToken	cancellationToken	The optional cancellation token to be used for cancelling the sequence at any time.

Returns

Type	Description
ValueTask<TSource>	The single element or the default value of TSource.

Type Parameters

Name	Description
TSource	The type of the elements of source.