تحديات برمجيةالتحدي الثاني - حل التمرين الثاني بلغة C#

using System;

class Program
{
    public static string ReplaceAll(string text, string find, string replacement)
    {
        int L1 = text.Length;
        int L2 = find.Length;

        string newText = "";

        for (int i = 0; i < L1;)
        {
            if (i <= L1 - L2 && text.Substring(i, L2).Equals(find))
            {
                newText += replacement;
                i += L2;
            }
            else
            {
                newText += text[i];
                i += 1;
            }
        }
        return newText;
    }

    static void Main(string[] args)
    {
        string text = "I like cats. I have one cat.";
        string find = "cat";
        string replacement = "dog";
        string newText = ReplaceAll(text, find, replacement);

        Console.WriteLine("Before: " + text);
        Console.WriteLine("After:  " + newText);

        Console.ReadKey();
    }

}

Before: I like cats. I have one cat.
After:  I like dogs. I have one dog.