Part 29 - Concat operator in LINQ

In this articlewe will discuss
1. The use of Concat operator
2. Difference between Concat and Union operators

Concat operator concatenates two sequences into one sequence.

The following code will concatenate both the integer sequences (numbers1 & numbers2) into one integer sequence. Notice that the duplicate elements ARE NOT REMOVED.

int[] numbers1 = { 1, 2, 3 };

int[] numbers2 = { 1, 4, 5 };

var result = numbers1.Concat(numbers2);

foreach (var v in result)

{

    Console.WriteLine(v);

}

Output :


Now let us perform a union between the 2 integer sequences (numbers1 & numbers2). Just like concat operator, union operator also combines the 2 integer sequences (numbers1 & numbers2) into one integer sequence, but notice that the duplicate elements ARE REMOVED.

int[] numbers1 = { 1, 2, 3 };

int[] numbers2 = { 1, 4, 5 };

var result = numbers1.Union(numbers2);

foreach (var v in result)

{

    Console.WriteLine(v);

}

Output :


What is the difference between Concat and Union operators?
Concat operator combines 2 sequences into 1 sequence. Duplicate elements are not removed. It simply returns the items from the first sequence followed by the items from the second sequence. 

Union operator also combines 2 sequences into 1 sequence, but will remove the duplicate elements.