01. Hogwarts

using System.Globalization;

string spellOgi = Console.ReadLine();

string commandOgi;

while ((commandOgi = Console.ReadLine()) != "Abracadabra")
{

    string[] commArg = commandOgi.Split(' ', StringSplitOptions.RemoveEmptyEntries);
    string curCommand = commArg[0];
    if (curCommand == "Abjuration")
    {
        spellOgi = spellOgi.ToUpper();
        Console.WriteLine(spellOgi);
    }
    else if (curCommand == "Necromancy")
    {
        spellOgi = spellOgi.ToLower();
        Console.WriteLine(spellOgi);

    }

    else if (curCommand == "Illusion")
    {
        int index = int.Parse(commArg[1]);
        if (index >= 0 && index < spellOgi.Length)
        {
            spellOgi = spellOgi.Remove(index, 1);

            string newChar = commArg[2];
            spellOgi = spellOgi.Insert(index, newChar);

            Console.WriteLine("Done!");
        }
        else
        {
            Console.WriteLine("The spell was too weak.");
        }

    }
    else if (curCommand == "Divination")
    {
        string firstString = commArg[1];
        string secondString = commArg[2];
        if (spellOgi.Contains(firstString))
        {
            spellOgi = spellOgi.Replace(firstString, secondString);
            Console.WriteLine(spellOgi);
        }

    }
    else if (curCommand == "Alteration")
    {
        string substring = commArg[1];
        if (spellOgi.Contains(substring))
        {
            int indexOfSub = spellOgi.IndexOf(substring);
            spellOgi = spellOgi.Remove(indexOfSub, substring.Length);
            Console.WriteLine(spellOgi);
        }
    }
    else
    {
        Console.WriteLine("The spell did not work!");
    }
}