Find multiplication of two numbers rapidly

RussianPeasantMultiplication.cs

using System;

public class Program {
  public static void Main() {
    int result = RussianPeasantMultiplication(121, 398);

    Console.WriteLine(result);
  }

  private static int RussianPeasantMultiplication(int number1, int number2) {
    int multiple = 0;

    multiple = AddToList(number1, number2, multiple);

    while (number1 != 1) {
      number1 /= 2;
      number2 *= 2;

      multiple = AddToList(number1, number2, multiple);
    }

    return multiple;
  }

  private static int AddToList(int number1, int number2, int multiple) {

    if (number1 % 2 != 0)
      multiple += number2;

    return multiple;
  }
}