Редици.03.01.How meny times a letter appears in a string

using System;
class SymbolAppearing
{
    static void Main()
    {
        string text = "Yambol and Vidin are beautiful cities";
        int index = 0, appearance = 0;
        Console.Write("Indexes: ");
        while((index = text.IndexOf('l', index)) != -1)
        {
            Console.Write(index++ + " ");
            appearance++;
        }
        Console.WriteLine();
        Console.WriteLine("Appearance: " + appearance);
    }
}