Method ExceptBy

ExceptBy<TSource, TKey>(IAsyncEnumerable<TSource>, IAsyncEnumerable<TSource>, Func<TSource, TKey>)

Returns the set of elements in the first sequence which aren't in the second sequence, according to a given key selector.

Declaration

public static IAsyncEnumerable<TSource> ExceptBy<TSource, TKey>(this IAsyncEnumerable<TSource> first, IAsyncEnumerable<TSource> second, Func<TSource, TKey> keySelector)

Parameters

Type	Name	Description
IAsyncEnumerable<TSource>	first	The sequence of potentially included elements.
IAsyncEnumerable<TSource>	second	The sequence of elements whose keys may prevent elements in first from being returned.
Func<TSource, TKey>	keySelector	The mapping from source element to key.

Returns

Type	Description
IAsyncEnumerable<TSource>	A sequence of elements from first whose key was not also a key for any element in second.

Type Parameters

Name	Description
TSource	The type of the elements in the input sequences.
TKey	The type of the key returned by keySelector.

Remarks

This is a set operation; if multiple elements in first have equal keys, only the first such element is returned. This operator uses deferred execution and streams the results, although a set of keys from second is immediately selected and retained.

Exceptions

Type	Condition
ArgumentNullException	first is null.
ArgumentNullException	second is null.
ArgumentNullException	keySelector is null.

ExceptBy<TSource, TKey>(IAsyncEnumerable<TSource>, IAsyncEnumerable<TSource>, Func<TSource, TKey>, IEqualityComparer<TKey>?)

Returns the set of elements in the first sequence which aren't in the second sequence, according to a given key selector.

Declaration

public static IAsyncEnumerable<TSource> ExceptBy<TSource, TKey>(this IAsyncEnumerable<TSource> first, IAsyncEnumerable<TSource> second, Func<TSource, TKey> keySelector, IEqualityComparer<TKey>? keyComparer)

Parameters

Type	Name	Description
IAsyncEnumerable<TSource>	first	The sequence of potentially included elements.
IAsyncEnumerable<TSource>	second	The sequence of elements whose keys may prevent elements in first from being returned.
Func<TSource, TKey>	keySelector	The mapping from source element to key.
IEqualityComparer<TKey>	keyComparer	The equality comparer to use to determine whether or not keys are equal. If null, the default equality comparer for TSource is used.

Returns

Type	Description
IAsyncEnumerable<TSource>	A sequence of elements from first whose key was not also a key for any element in second.

Type Parameters

Name	Description
TSource	The type of the elements in the input sequences.
TKey	The type of the key returned by keySelector.

Remarks

This is a set operation; if multiple elements in first have equal keys, only the first such element is returned. This operator uses deferred execution and streams the results, although a set of keys from second is immediately selected and retained.

Exceptions

Type	Condition
ArgumentNullException	first is null.
ArgumentNullException	second is null.
ArgumentNullException	keySelector is null.
ArgumentNullException	keyComparer is null.