Enumerable.Intersect<TSource> Method (IEnumerable<TSource>, IEnumerable<TSource>)
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Produces the set intersection of two sequences by using the default equality comparer to compare values.
Assembly: System.Core (in System.Core.dll)
public static IEnumerable<TSource> Intersect<TSource>( this IEnumerable<TSource> first, IEnumerable<TSource> second )
The type of the elements of the input sequences.
- Type: System.Collections.Generic.IEnumerable<>
An IEnumerable<T> whose distinct elements that also appear in second will be returned.
Return ValueType: System.Collections.Generic.IEnumerable<>
A sequence that contains the elements that form the set intersection of two sequences.
Usage NoteIn Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<>. When you use instance method syntax to call this method, omit the first parameter.
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.
The default equality comparer, Default, is used to compare values of the types that implement the IEqualityComparer<T> generic interface. To compare a custom data type, you need to implement this interface and provide your own GetHashCode and Equals methods for the type.
The following code example demonstrates how to use to return the elements that appear in each of two sequences of integers.
If you want to compare sequences of objects of a custom data type, you have to implement the IEqualityComparer<T> generic interface in the class.