Enumerable.Intersect<TSource> Method (IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)

July 28, 2014

Produces the set intersection of two sequences by using the specified IEqualityComparer<T> to compare values.

Namespace:  System.Linq
Assembly:  System.Core (in System.Core.dll)

public static IEnumerable<TSource> Intersect<TSource>(
	this IEnumerable<TSource> first,
	IEnumerable<TSource> second,
	IEqualityComparer<TSource> comparer
)

Type Parameters

TSource

The type of the elements of the input sequences.

Parameters

first
Type: System.Collections.Generic.IEnumerable<TSource>
An IEnumerable<T> whose distinct elements that also appear in second will be returned.
second
Type: System.Collections.Generic.IEnumerable<TSource>
An IEnumerable<T> whose distinct elements that also appear in the first sequence will be returned.
comparer
Type: System.Collections.Generic.IEqualityComparer<TSource>
An IEqualityComparer<T> to compare values.

Return Value

Type: System.Collections.Generic.IEnumerable<TSource>
A sequence that contains the elements that form the set intersection of two sequences.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<TSource>. When you use instance method syntax to call this method, omit the first parameter.

ExceptionCondition
ArgumentNullException

first or second is null.

This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

The intersection of two sets A and B is defined as the set that contains all the elements of A that also appear in B, but no other elements.

When the object returned by this method is enumerated, Intersect enumerates first, collecting all distinct elements of that sequence. It then enumerates second, marking those elements that occur in both sequences. Finally, the marked elements are yielded in the order in which they were collected.

If comparer is null, the default equality comparer, Default, is used to compare values.

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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