When we need to generate a sequence of integer values, we can do it manually using some kind of loop, or we make use of the Enumerable.Range method.
The following code illustrates:
var oneToTen = Enumerable.Range(1, 10);
int twentyToThirty = Enumerable.Range(20, 11).ToArray();
List<int> oneHundredToOneThirty = Enumerable.Range(100, 31).ToList();
We can also use the results of .Range and transform them in some way, for example to get the letters of the alphabet we could write something like this:
var alphabet = Enumerable.Range(0, 26).Select(i => Convert.ToChar('A' + i));
This will generate an IEnumerable<char> containing the letters A through Z.
(The .Range method is one of a smorgasbord of C# Tips and Traps that I cover in my Pluralisight C# courses.)