using System.Text.RegularExpressions;
Regex re = new Regex(@"([a-zA-Z]+)(\d+)");
Match result = re.Match(input);
string alphaPart = result.Groups[1].Value;
string numberPart = result.Groups[2].Value;
string str = "12AB34CD";
char[] arr = str.ToCharArray();
foreach (char ch in arr)
{
Console.WriteLine(ch);
}
Console.ReadLine();