How to use String Builder in C#

How to use String Builder in C#

using System;
using System.Text;

class Program
{
    static void Main()
    {
       StringBuilder builder = new StringBuilder();
       // Append to StringBuilder.
       for (int i = 0; i < 10; i++)
       {
            builder.Append(i).Append(" ");
       }
       Console.WriteLine(builder);
    }
}