LeftPad in C#

using System;
using System.Text;
public class LeftPad
{
  public static String leftPad(String str,
                               int paddedLength,
                               char ch = '.') {
    if (paddedLength <= str.Length) {
      return str;
    }
    StringBuilder sb = new StringBuilder();
    paddedLength = paddedLength - str.Length;
    for (int i = 0; i < paddedLength; ++i) {
      sb.Append(ch);
    }
    sb.Append(str);
    return sb.ToString();
  }
  public static void Main() {
    Console.WriteLine(leftPad("1", 1));
    Console.WriteLine(leftPad("2", 2));
    Console.WriteLine(leftPad("3", 3));
    Console.WriteLine(leftPad("4", 4));
    Console.WriteLine(leftPad("5", 5));
    Console.WriteLine(leftPad("hello", 7));
    Console.WriteLine(leftPad("foo",  6));
    Console.WriteLine(leftPad("foo", 3));
    Console.WriteLine(leftPad("foobar", 3));
    Console.WriteLine(leftPad("foo", 6, '?'));
  }
}