Intersect. This is an extension method from the System.Linq namespace. In set theory, an intersection is the subset of each collection that is found in both collections.

Extension

HashSet

SortedSet

C# method details. Intersect gets common elements from 2 collections. The Intersect method here is elegant—it can be used on many types of elements.

This program invokes the Intersect method. The two using directives at the top of the program specify where the types are located. We use the array initializer syntax.

Array Initialize

Array

int

using System;
using System.Linq;

class Program
{
    static void Main()
    {
        // Assign two arrays.
        int[] array1 = { 1, 2, 3 };
        int[] array2 = { 2, 3, 4 };
        // Call Intersect extension method.
        var intersect = array1.Intersect(array2);
        // Write intersection to screen.
        foreach (int value in intersect)
        {
            Console.WriteLine(value);
        }
    }
}
2
3

A summary. We examined the Intersect method. We computed the intersecting part of two integer arrays using a declarative syntax, rather than an imperative loop construct.

A final tip. A declarative syntax is more concise. But an imperative style could improve the efficiency of this particular operation.