This linq query should do it:
strArray.Select(s => int.Parse(s)).ToArray()
int[] a = Array.ConvertAll("123,456".Split(','), s => Int32.Parse(s));
Should do just fine. You could modify the lambda to use TryParse if you don't want exceptions.
int[] a = "123,456".Split(’,’).Select(s => int.Parse(s)).ToArray();