using System.Collections;
using System.Collections.Generic;
using System.Text.RegularExpressions;
public static void Main()
List<string> li = new List<string>();
li.Add("Output-PROD-EUR-VI-VI1PR08OC0020-20180410_20_26_09-hadoop.log.txt");
li.Add("Output-PROD-EUR-VI-VI1PR08OC0020-20180410_20_06_09-CodePackage-MoonWorkflow-Expansion.txt");
li.Add("Output-PROD-EUR-VI-VI1PR08OC0020-20180410_20_03_17_AuthenticateHiveUserWithKdcRuntime_attempt1.txt");
li.Add("Errors-PROD-EUR-VI-VI1PR08OC0020-20180410_20_24_23_TerminateRunningYarnApplicationsRuntime.txt");
for (int i =0 ; i< li.Count() ; i++ )
Match match = Regex.Match(keyy, @"\d{8}_\d{2}_\d{2}_\d{2}");
string date = match.Value;
li[i] = keyy.Split('-')[0] +"-"+ date + keyy.Replace(keyy.Split('-')[0],"").Replace("-"+date,"");
Console.WriteLine(li[i]);