How to make nullable list of int

Question

I have this string:

string alertsId = "1,2,3,4";

Then I convert the string to list of ints:

List<int> list = alertsId.Split(',').Select(n => Convert.ToInt32(n)).ToList();

How can I convert the list above to nullable list of ints?

Answer 1

Well a List<int> is a reference type and therefor nullable by definition. So I guess you want to create a list of nullable integers (List<int?>).

You can simply use Cast<T>():

List<int?> nullableList = list.Cast<int?>().ToList();

Or to create it directly:

List<int?> list = alertsId.Split(',').Select(n => (int?)Convert.ToInt32(n)).ToList();

Answer 2

Define a function:

public int? ParseToNullable(string s)
{
    int? result = null;
    int temp = 0;
    if (int.TryParse(s, out temp)) 
    {
         result = temp;
    }
    return result;
}

And then use it like this:

string alertsId = "1,2,3,4";
List<int?> list = alertsId.Split(',').Select(n => ParseToNullable(n)).ToList();