Is there a specific way to user input a value using a separator such as "#"?

I have the below code which is supposed to ask for a user input values to be entered of various integers separated by "#" like 1#2#3##2 and so on. It is then eventually supposed to find the values in the sequence entered that have repeats and display it like "the sequence contains 2 repeated value."

However I am not sure if the code I have used to separate the user entered value is correct as it displays an error:

public class Program
{
    public static void Main(string[] args)
    {  
        // Keep the following line intact 
        Console.WriteLine("===========================");

        // Insert your solution here.     
               
        // user input gets the input from the user 
       
        // regarding a line where integers are separated by # 
       
        String userInput;

        Console.WriteLine("Please enter single line containing a list of integers, separated by '#':");

        userInput = Console.ReadLine();

        // splitting the userInput into Array of Strings  
        if (userInput != null)
        {
            // splitting the userInput by # 
            String[] numberStrings = userInput.Split("#");

            // numbers list contain the list of unique numbers
            List<int> numbers = new List<int>();

            // takes count of duplicate numbers 
            int totalDuplicateNumbers = 0;

            // adding the number string to the list after converting to int
        
            for (int i = 0; i < numberStrings.Length; i++)
            {
                numbers.Add(Int32.Parse(numberStrings[i]));
            }

            // now sorting the number list     
            numbers.Sort();

            bool duplicatePresent = false;

            for (int i = 0; i < numbers.Count - 1; i++)
            {
                if (numbers[i] == numbers[i + 1])
                {
                    if (!duplicatePresent)
                    {
                        duplicatePresent = true;

                        totalDuplicateNumbers += 1;
                    }
                }
                else
                {
                    duplicatePresent = false;
                }
            }

            // display result        
    
            Console.WriteLine($"The sequence contains {totalDuplicateNumbers} repeated values.");
        }
        else
        {
            Console.WriteLine("Wrong input");
        }

        // Keep the following lines intact

        Console.WriteLine("===========================");
    }
}

>Solution :

Your code is not correct. Split expects one or more characters to split by. You passed a string. Pass a character, like this:

String[] numberStrings = userInput.Split('#');

Please note that this solution will fail on your test input of

1#2#3##2

Because that means that there are the strings "1", "2", "3", "", "2" and "" will fail in your subsequent parsing attempt.

You may want to try

String[] numberStrings = userInput.Split('#', StringSplitOptions.RemoveEmptyEntries);

This removes the empty, non-number entries. Whether that is what your exercise wants you to do, or if you should do something else with the empty input, is something only you can answer.