You should use a foreach loop, like this:
public static IEnumerable<int> StringToIntList(string str) {
if (String.IsNullOrEmpty(str))
yield break;
foreach(var s in str.Split(',')) {
int num;
if (int.TryParse(s, out num))
yield return num;
}
}
Note that like your original post, this will ignore numbers that couldn’t be parsed.
If you want to throw an exception if a number couldn’t be parsed, you can do it much more simply using LINQ:
return (str ?? "").Split(',').Select<string, int>(int.Parse);