LINQ | Concatenation Operator | Concat

The concatenation is a process in which one sequence is appended into another sequence. In LINQ, the concatenation operation contains only one operator that is known as Concat. It is used to append two same types of sequences or collections and return a new sequence or collection.

  • It does not support query syntax in C# and VB.NET languages.
  • 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.
  • It allow duplicate elements.

As shown in the below image, here two sequences of the same types are concatenated into one sequence.

Example 1:

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// C# program to concatenate the
// given sequences
using System;
using System.Linq;
  
class GFG {
  
    static public void Main()
    {
  
        // Data source
        char[] sequence1 = {'p', 'q', 'r', 's', 'y', 'z'};
        char[] sequence2 = {'p', 'm', 'o', 'e', 'c', '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);
        }
  
        // Concatenate the given array
        // Using Concat function
        var result = sequence1.Concat(sequence2);
  
        Console.WriteLine("New Sequence:");
        foreach(var val in result)
        {
            Console.WriteLine(val);
        }
    }
}

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Output:

Sequence 1 is: 
p
q
r
s
y
z
Sequence 2 is: 
p
m
o
e
c
z
New Sequence:
p
q
r
s
y
z
p
m
o
e
c
z

Example 2:

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// C# program to print the major 
// language of 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;
    }
}
  
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 = 219, emp_name2 = "Anita",
                                           emp_lang2 = "Scala"},
  
            new Employee2() {emp_id2 = 223, emp_name2 = "Manya",
                                          emp_lang2 = "Python"},
  
            new Employee2() {emp_id2 = 266, emp_name2 = "Rohan",
                                            emp_lang2 = "Ruby"},
  
        };
  
        // Query to concatenate the major
        // languages of the employees of 
        // two different departments
        // Using Concat method
        var res = emp1.Select(e => e.emp_lang1).Concat(emp2.Select(e => e.emp_lang2));
  
        Console.WriteLine("Major Languages Used are: ");
          
        foreach(var val in res)
        {
            Console.WriteLine(val);
        }
    }
}

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Output:

Major Languages Used are: 
C#
C
Java
Scala
Python
Ruby


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