LINQ | Set Operator | Intersect

In LINQ, Set operators are those operators in query expression which return a result set which is based on the existence or non-existence of the equivalent elements within the same or different collections or sequences or sets. The standard query operator contains the following set operators:

  1. Union
  2. Intersect
  3. Except
  4. Distinct

Intersect Operator

The Intersect operator returns the set intersection. Or in other words, we can say that it return the set or collection which contain the common elements appears in two collections, or sets.



  • It does not support query syntax in C# and VB.Net languages. But you can use Intersect method on query variable or you can wrap your query in brackets and then the call Intersect method.
  • It support method syntax in both C# and VB.Net languages.
  • It present in both the Queryable and Enumerable class.
  • It is implemented by using deferred execution.
  • When you are working with the collections of complex types, then you must use IEqualityComparer interface, otherwise the Intersect method will give you incorrect result.

Example 1:

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// C# program to find the intersection
// of the given sequence
using System;
using System.Linq;
  
class GFG {
  
    static public void Main()
    {
  
        // Data source
        char[] sequence1 = {'m', 'q', 'o',
                           's', 'y', 'a'};
  
        char[] sequence2 = {'p', 't', 'r'
                           's', 'y', 'z'};
  
        // Display the sequences
        Console.WriteLine("Sequence 1 is: ");
  
        foreach(var s1 in sequence1)
        {
            Console.WriteLine(s1);
        }
  
        Console.WriteLine("Sequence 2 is: ");
  
        foreach(var s2 in sequence2)
        {
            Console.WriteLine(s2);
        }
  
        // Get intersection of the given sequence
        // Using Intersect function
        var result = sequence1.Intersect(sequence2);
  
        Console.WriteLine("New Sequence: ");
  
        foreach(var val in result)
        {
            Console.WriteLine(val);
        }
    }
}

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Output:

Sequence 1 is: 
m
q
o
s
y
a
Sequence 2 is: 
p
t
r
s
y
z
New Sequence: 
s
y

Example 2:

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// C# program to find the commonly
// known languages by the employees
using System;
using System.Linq;
using System.Collections.Generic;
  
// Employee details
public class Employee1 {
  
    public int emp_id1
    {
        get;
        set;
    }
  
    public string emp_name1
    {
        get;
        set;
    }
    public string emp_lang1
    {
        get;
        set;
    }
}
  
// Employee details
public class Employee2 {
  
    public int emp_id2
    {
        get;
        set;
    }
  
    public string emp_name2
    {
        get;
        set;
    }
    public string emp_lang2
    {
        get;
        set;
    }
}
  
public class GFG {
  
    // Main method
    static public void Main()
    {
        List<Employee1> emp1 = new List<Employee1>() {
  
            new Employee1() {emp_id1 = 209, emp_name1 = "Anjita",
                                               emp_lang1 = "C#"},
  
            new Employee1() {emp_id1 = 210, emp_name1 = "Soniya",
                                                emp_lang1 = "C"},
  
            new Employee1() {emp_id1 = 211, emp_name1 = "Rohit",
                                            emp_lang1 = "Java"},
  
        };
  
        List<Employee2> emp2 = new List<Employee2>() {
  
            new Employee2() {emp_id2 = 290, emp_name2 = "Anjita",
                                               emp_lang2 = "C#"},
  
            new Employee2() {emp_id2 = 212, emp_name2 = "MaMa",
                                         emp_lang2 = "Python"},
  
            new Employee2() {emp_id2 = 233, emp_name2 = "Rima",
                                           emp_lang2 = "Java"},
  
        };
  
        // Query to find the commonly known
        // languages by the employees
        // Using Intersect method
        var res = emp1.Select(e => e.emp_lang1).Intersect(emp2.Select(e => e.emp_lang2));
          
        Console.WriteLine("Commonly known Languages: ");
          
        foreach(var val in res)
        {
            Console.WriteLine(val);
        }
    }
}

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Output:

Commonly known Languages: 
C#
Java


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