C# String Formatting and StringBuilder

using System;
using System.Text;

class Program
{
    static void Main()
    {
        int n = 42;
        Console.WriteLine($"{n,6}|");
        Console.WriteLine($"{n,-6}|");
        Console.WriteLine($"{n:D5}");
        Console.WriteLine($"{255:X}");
        Console.WriteLine(string.Format("{0} and {1}", "a", "b"));

        StringBuilder sb = new StringBuilder();
        for (int i = 1; i <= 3; i++)
        {
            sb.Append("[").Append(i).Append("]");
        }
        sb.AppendLine();
        sb.Append("end");
        Console.WriteLine(sb.ToString());
        Console.WriteLine(sb.Length);
        Console.WriteLine("abc".PadLeft(5, '*'));
        Console.WriteLine(string.IsNullOrEmpty(""));
    }
}

    42|
42    |
00042
FF
a and b
[1][2][3]
end
13
**abc
True