I am having trouble debugging my code. I found this code in a book example in an incomplete form and containing syntax error and logical errors and I tried my best to debug it and correct these errors. But unfortunately I could not figure out errors even using the debugger. What changes should I need to do in order to correct this code?

namespace Exercise_9
{
    class Program
    {
        static void Main(string[] args)
        {
            //make some sets
            //Note, this is where I make the correction within the code. 
            //Originally, this was written as Set A = new Set(); and
            // Set B = new Set(); 

            //Here is the correction by assigning the set variable 
            Set A = new Set();
            Set B = new Set();

            //put some stuff in the sets
            Random r = new Random();
            for (int i = 0; i < 10; i++)
            {
                A.addElement(r.Next(4));
                B.addElement(r.Next(12));
            }

            //display each set and the union
            Console.WriteLine("A: " + A);
            Console.WriteLine("B: " + B);
            Console.WriteLine("A union B: " + A.union(B)); //note, I believe this isnt a proper notation. 

            //display original sets (should be unchanged)
            Console.WriteLine("After union operation");
            Console.WriteLine("A: " + A);
            Console.WriteLine("B: " + B);

        }
    }

}