Method FindLastIndex

FindLastIndex<TSource>(IAsyncEnumerable<TSource>, Func<TSource, bool>, CancellationToken)

Searches for an element that matches the conditions defined by the specified predicate and returns the zero-based index of the last occurrence within the entire IAsyncEnumerable<T>.

Declaration

public static ValueTask<int> FindLastIndex<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken = default)

Parameters

Type	Name	Description
IAsyncEnumerable<TSource>	source	The source sequence.
Func<TSource, bool>	predicate	The predicate that defines the conditions of the element to search for.
CancellationToken	cancellationToken	The optional cancellation token to be used for cancelling the sequence at any time.

Returns

Type	Description
ValueTask<int>	The zero-based index of the last occurrence of an element that matches the conditions defined by predicate within the entire IAsyncEnumerable<T>, if found; otherwise, -1.

Type Parameters

Name	Description
TSource	The type of elements of source

Remarks

The IAsyncEnumerable<T> is searched forward starting at the first element and ending at the last element, and the index of the last instance of an element that matches the conditions defined by predicate is returned.

The predicate is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. The elements of the current IAsyncEnumerable<T> are individually passed to the predicate delegate.

This operator executes immediately.

Exceptions

Type	Condition
ArgumentNullException	source or predicate is null.

FindLastIndex<TSource>(IAsyncEnumerable<TSource>, Func<TSource, bool>, Index, CancellationToken)

Searches for an element that matches the conditions defined by the specified predicate and returns the zero-based index of the last occurrence within the range of elements in the IAsyncEnumerable<T> that extends backwards from the specified index to the first element.

Declaration

public static ValueTask<int> FindLastIndex<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, Index index, CancellationToken cancellationToken = default)

Parameters

Type	Name	Description
IAsyncEnumerable<TSource>	source	The source sequence.
Func<TSource, bool>	predicate	The predicate that defines the conditions of the element to search for.
Index	index	The Index of the ending element within the sequence.
CancellationToken	cancellationToken	The optional cancellation token to be used for cancelling the sequence at any time.

Returns

Type	Description
ValueTask<int>	The zero-based index of the last occurrence of an element that matches the conditions defined by predicate within the the range of elements in the IAsyncEnumerable<T> that extends backwards from index to the first element, if found; otherwise, -1.

Type Parameters

Name	Description
TSource	The type of elements of source

Remarks

The IAsyncEnumerable<T> is searched forward starting at the first element and ending at index, and the index of the last instance of an element that matches the conditions defined by predicate is returned.

The predicate is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. The elements of the current IAsyncEnumerable<T> are individually passed to the predicate delegate.

This operator executes immediately.

Exceptions

Type	Condition
ArgumentNullException	source or predicate is null.

FindLastIndex<TSource>(IAsyncEnumerable<TSource>, Func<TSource, bool>, Index, int, CancellationToken)

Searches for an element that matches the conditions defined by the specified predicate and returns the zero-based index of the last occurrence within the range of elements in the IAsyncEnumerable<T> that ends at the specified index to the last element and contains the specified number of elements.

Declaration

public static ValueTask<int> FindLastIndex<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, Index index, int count, CancellationToken cancellationToken = default)

Parameters

Type	Name	Description
IAsyncEnumerable<TSource>	source	The source sequence.
Func<TSource, bool>	predicate	The predicate that defines the conditions of the element to search for.
Index	index	The Index of the ending element within the sequence.
int	count	The number of elements in the section to search.
CancellationToken	cancellationToken	The optional cancellation token to be used for cancelling the sequence at any time.

Returns

Type	Description
ValueTask<int>	The zero-based index of the last occurrence of an element that matches the conditions defined by predicate within the the range of elements in the IAsyncEnumerable<T> that that ends at index and contains count number of elements, if found; otherwise, -1.

Type Parameters

Name	Description
TSource	The type of elements of source

Remarks

The IAsyncEnumerable<T> is searched forward starting at the first element and ending at index, and the index of the last instance of an element that matches the conditions defined by predicate no earlier in the sequence than count items before index is returned.

The predicate is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. The elements of the current IAsyncEnumerable<T> are individually passed to the predicate delegate.

This operator executes immediately.

Exceptions

Type	Condition
ArgumentNullException	source or predicate is null.
ArgumentOutOfRangeException	count is less than 0.