Initializing String Builder with a string in C#
You can assign a string to String Builder while you are creating it. 

using System;
using System.Text;

namespace forgetCode
{    
    class program
    {        
        public static void Main()
        {            

            StringBuilder sb = new StringBuilder("Time is gold");

            Console.WriteLine(sb.ToString());
               
        }
    }
}


Output:
Time is gold