Question

I need to convert a string of comma separated integers into a list of integers.

What is the best way to do this?

I can do it below but am worried about the performance – Is there a better more efficient way to do this?

public IEnumerable<int> GetListOfIds()
{
    string Ids = "1,4,5,7,12"; // would be passed into method
    List<int> _result = Ids.Split(',')
                           .ToList()
                           .Select(item => int.Parse(item))
                           .ToList();

    return _result;
}

Answer 1

There’s no need to call ToList, but otherwise your code looks fine:

public IEnumerable<int> GetListOfIds(string ids)
{
    return ids.Split(',').Select(item => int.Parse(item));
}

You may also want to consider adding error handling in case the input string is invalid:

public IEnumerable<int> GetListOfIds(string ids)
{
    foreach (string part in ids.Split(','))
    {
        int x;
        if (!int.TryParse(part, out x))
        {
            throw new ArgumentException(
                string.Format("The value {0} cannot be parsed as an integer.", part),
                "ids");
        }
        else
        {
            yield return x;
        }
    }
}