using System;

using System.Linq;

using System.Text;

public class Program

{

    private static Random random = new Random();

    //Used to generate random string. Not for your use

    public static string RandomString(int length)

    {

        const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

        return new string(Enumerable.Repeat(chars, length)

          .Select(s => s[random.Next(s.Length)]).ToArray());

    }

    //Your constructor with StringBuilder

    public Program(StringBuilder sb) => Console.WriteLine(sb.ToString());

    public static void Main()

    {

        var firstStr = "Prasad ";

        for(int i = 0; i < 10; i++)

        {   

            var randomStr = RandomString(6);

            var sb = new StringBuilder(firstStr + randomStr);

            //Creating instance and passing string builder

            var newInstance = new Program(sb);

        }

    }

}