Get Substring – everything before and after certain characters [closed]

You could use regular expressions, e.g:

class Program
{
    static void Main(string[] args)
    {
        var input = " SUCCESS Post Policy Success INVOICE No. :: WS1704003404 || Policy No :: 59203313 || App No. :: 123456724 ";

        var pattern = @"::\s*(\w+)\s*";

        var matches = Regex.Matches(input, pattern);

        foreach (Match match in matches)
            Console.WriteLine(match.Groups[1].Value);

    }
}