Find all integers in list of strings

Question

Given this list of string values:

"12345", "6789a", "9876", "23467b"

How do we use a Linq statement in C# to select only the integers? In other words, we only want to return 12345 and 9876.

Answer 1

You can filter your entries based on the return value of the Int32.TryParse method:

int temp;
list.Where(x => int.TryParse(x, out temp));

Answer 2

Filter the list down to only those strings all characters of which are digits:

var filtered = list.Where(s => s.All(char.IsDigit));

An alternative is to use int.TryParse as the filtering function, which has a number of subtle differences in behavior (the rules for what a valid integer is allow more than just digits, see the documentation).

If you want the results typed as integers, follow this up with .Select(int.Parse).