using System.Text.RegularExpressions;
public static void Main()
string[] keys = new string[] {
"FOR TESTING/20220809-222-SUCAT.csv",
"FOR TESTING/20220809-223-MARIKINA.csv"
Regex _regex = new Regex(
pattern: "^[0-9]{8}-[0-9]{3}-\\w+.csv",
options: RegexOptions.Compiled | RegexOptions.IgnoreCase);
foreach(var s3Object in keys)
var idx = s3Object.LastIndexOfAny(new char[] { '\\', '/' }) + 1;
if(idx >= 0 && _regex.IsMatch(s3Object, startat: idx))
Console.WriteLine($"{s3Object} is match ({s3Object[idx..]}).");
Console.WriteLine($"{s3Object} is not match ({s3Object[idx..]}).");