Here is my c# attempt, feel free to provide feedback, use or comment.

using System.Text.RegularExpressions;

static void Main(String[] args) {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution */
    int n = -1;
    string input = "";
    char[] trimM = {'(', ')'};
    List<string> texts = new List<string>();
    string[] operations, separate;
    string combine = "";
    input = Console.ReadLine();
    while(input != null)
    {
        texts.Add(input);
        input = Console.ReadLine();
    }
    foreach(string s in texts){
        operations = s.Split(";");
        switch(operations[0])
        {
            case "S":
                if(operations[1] == "M")
                    operations[2] = operations[2].Trim(trimM);
                separate = Regex.Split(operations[2], @"(?<!^)(?=[A-Z])");
                foreach(string word in separate)
                {
                    if(separate.Last() == word)
                        Console.WriteLine(word.ToLower());
                    else
                        Console.Write(word.ToLower() + " ");
                }
                break;
            case "C":
                separate = operations[2].Split(" ");
                foreach(string word in separate)
                {
                    if(word == separate.First())
                    {
                        if(operations[1] == "C")
                            combine += word[0].ToString().ToUpper() + word.Substring(1);
                        else
                            combine += word;
                    }
                    else
                    {
                        combine += word[0].ToString().ToUpper() + word.Substring(1);
                    }
                }
                if(operations[1] == "M")
                        combine += "()";
                Console.WriteLine(combine);
                combine = "";
                break;
        }
    }
}

}