Regex (edit)

https://laptrinhvb.net/bai-viet/chuyen-de-csharp/Huong-dan-tach-so-ra-khoi-chuoi-su-dung-Regular-Expression--Csharp-/b7bd559e9ae9bd63.html

string input = "[1,2,3,4,5,99]";
Regex regexObj = new Regex(@"(\d+)([^0-9]+)", RegexOptions.IgnorePatternWhitespace);
Match match = regexObj.Match(input);
while (match.Success)
{
    Console.WriteLine(match.Groups[1].Value);
    match = match.NextMatch();
}

https://viblo.asia/p/tim-hieu-ve-xu-ly-chuoi-bang-regex-phan-cuoi-vyDZOQz75wj

https://viblo.asia/p/tim-hieu-ve-xu-ly-chuoi-bang-regex-phan-ii-YWOZrMYRKQ0