using System;
using System.Text;
public class App
{
static void Main()
{
StringBuilder sb = new StringBuilder("ABC", 50);
sb.Append(new char[] { 'D', 'E', 'F' });
sb.AppendFormat("GHI{0}{1}", 'J', 'k');
Console.WriteLine("{0} chars: {1}", sb.Length, sb.ToString());
sb.Insert(0, "asdf: ");
sb.Replace('k', 'K');
Console.WriteLine("{0} chars: {1}", sb.Length, sb.ToString());
}
}