Save yourself some pain…
using System.Linq;
int[] ints = new [] { 10, 20, 10, 34, 113 };
List<int> lst = ints.OfType<int>().ToList(); // this isn't going to be fast.
Can also just…
List<int> lst = new List<int> { 10, 20, 10, 34, 113 };
or…
List<int> lst = new List<int>();
lst.Add(10);
lst.Add(20);
lst.Add(10);
lst.Add(34);
lst.Add(113);
or…
List<int> lst = new List<int>(new int[] { 10, 20, 10, 34, 113 });
or…
var lst = new List<int>();
lst.AddRange(new int[] { 10, 20, 10, 34, 113 });