Question

I have a file with int values in each line (although it’s possible that some values are not ints like some comments). But the structure of the file is:

1
2
3
4
5
6
7
#some comment
9
10
etc...

What’s the fastest way to convert it to IEnumerable. I could read line by line and use List and call Add method, but I guess it’s not the best in terms of performance.

Thanks

Answer 1

You could create your IEnumerable on-the-fly while reading the file:

IEnumerable<Int32> GetInts(string filename)
{
    int tmp = 0;
    foreach(string line in File.ReadLines(filename))
        if (Int32.TryParse(line, out tmp))
            yield return tmp;
}

This way, you can do whatever you want to do with your integers while reading the file, using a foreach loop.

foreach(int i in GetInts(@"yourfile"))
{
    ... do something with i ...
}

---

If you just want to create a list, simply use the ToList extension:

List<Int32> myInts = GetInts(@"yourfile").ToList();

but there probably won’t be any measurable performance difference if you “manually” create a list as you described in your question.