System Text C# by API

using System;
   using System.Text;
   class StringBuilderFeatures
   {
      static void Main(string[] args)
      {
         StringBuilder buffer =new StringBuilder( "Hello, how are you?" );
         string output = "buffer = " + buffer.ToString() +
            "\nLength = " + buffer.Length +
            "\nCapacity = " + buffer.Capacity;
         buffer.EnsureCapacity( 75 );
         output += "\n\nNew capacity = " +buffer.Capacity;
         // truncate StringBuilder by setting Length property
         buffer.Length = 10;
         output += "\n\nNew length = " +
            buffer.Length + "\nbuffer = ";
         // use StringBuilder indexer
         for ( int i = 0; i < buffer.Length; i++ )
            output += buffer[ i ];
         Console.WriteLine( output);
      }
   }