Concatenate two IEnumerable sequences in C# .NET

We can use the Range method to build two integer sequences as follows:

IEnumerable<int> firstRange = Enumerable.Range(10, 10);
IEnumerable<int> secondRange = Enumerable.Range(5, 20);

You can join the two sequences using the Concat method:

List<int> concatenated = firstRange.Concat(secondRange).ToList();
concatenated.ForEach(i => Debug.WriteLine(i));

You’ll see that the concatenated sequence holds all numbers from the first and the second sequence:

10
11
12
13
14
15
16
17
18
19
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24

If that’s not what you want then you can filter out the duplicates using the Union extension method:

List<int> concatenated = firstRange.Union(secondRange).ToList();
concatenated.ForEach(i => Debug.WriteLine(i));

…and here come all unique values:

10
11
12
13
14
15
16
17
18
19
5
6
7
8
9
20
21
22
23
24

View the list of posts on LINQ here.