13. Strings and Text Processing 5. ToUpperTextBetweenTags

using System;


class ToUpperTextBetweenTags
{
    static void Main()
    {
        string str = @"We are living in a <upcase>yellow submarine</upcase>. We don't have <upcase>anything</upcase> else.";
        int startIndex = 0;
        int endIndex = 0;
        Console.WriteLine(str);

        for (int i = 0; i < str.Length - 8; i++)
        {
            if (str.Substring(i, 8) == "<upcase>")
            {
                startIndex = i + 8;
                i = startIndex;
            }
            if (str.Substring(i, 9) == "</upcase>")
            {
                endIndex = i;
                int length = endIndex - startIndex;
                string upperStr = str.Substring(startIndex, length).ToUpper();
                //Console.WriteLine(upperStr);
                str = str.Remove(startIndex, length);
                //Console.WriteLine(str);
                str = str.Insert(startIndex, upperStr);
                //Console.WriteLine(str);
                str = str.Remove(startIndex - 8, 8);
                str = str.Remove(endIndex-8, 9);
            }
        }
        Console.WriteLine(str);
    }
}