using System;
using System.IO;
using System.Text.RegularExpressions;
using System.Linq;
public class Test
{
public static void Main()
{
var line = "a, s, f, double, double, 12, sd, 1";
var latIndex = 5;
var pat = $@"^((?:[^,]*,){{{latIndex+1}}})(.*)";
Console.WriteLine(pat);
var veiRef = "str";
line = Regex.Replace(line, pat, $"${{1}}{veiRef.Replace("$","$$")}$2");
Console.WriteLine(line);
}
}
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
^((?:[^,]*,){6})(.*)
a, s, f, double, double, 12,str sd, 1