Accessing individual words in user input (Console.Readline())

namespace A2
{
    // Define a section to hold all the info that prompts the user to provide responses upon first opening the project.
    public class UserInput
    {
        static void Main()
        {
            // First we must print a statement that can be anything to welcome the user to the macchine thing
            // Write out custom message to the UI
            Console.WriteLine($"Welcome to the Tom's Obstacle Avoidance System!");
            // Write out the valid commands
            Console.WriteLine($"Valid commands are:");
            Commands.ListCommands();
            // List other options
            Console.WriteLine($"help: displays this help message");
            Console.WriteLine($"exit: closes this program");

            // While loop that keeps running while true (while the use hasnt yet entered exit) that checks
            // the validity/input of the user.
            while (true)
            {
                // Prompt the user to enter a command.
                Console.WriteLine($"Enter command:");
                // Read the users input
                string UserInput = Console.ReadLine();
                // If the user says exit, then we terminate the program
                // Check if it is exit first to avoid unnessary iterating of the valid commands list if it is "exit"
                if (UserInput == "exit")
                {
                    // Terminate
                    break;
                }

                // If the user enters something else other than exit, then we can check if it is a valid command
                if (!Commands.ValidCommands.Contains(UserInput))
                {
                    // Inform the user that their input is invalid, returning their input back to them.
                    Console.WriteLine("Invalid option: {0}", UserInput);
                    // Prompting the help message
                    Console.WriteLine($"Type 'help' to see a list of commands.");
                }

                if (UserInput == "help")
                {
                    Console.WriteLine($"Valid commands are:");
                    Commands.ListCommands();
                    Console.WriteLine($"help: displays this help message");
                    Console.WriteLine($"exit: closes this program");
                }

                if (UserInput == "add")
                {
                    switch (UserInput)
                    {
                        case "gaurd":
                            Console.WriteLine($"Chosen Gaurd");
                            break;
                        case "fence":
                            Console.WriteLine($"Chosen Fence");
                            break;
                        case "sensor":
                            Console.WriteLine($"Chosen Sensor");
                            break;
                        case "camera":
                            Console.WriteLine($"Chosen Camera");
                            break;
                    }
                }   
                    else
                    Console.WriteLine($"You need to specify an obstacle type.");
                    if (!Obstacles.ValidObstacles.Contains(UserInput))
                        // Inform the user that their input is invalid, returning their input back to them.
                        Console.WriteLine("Invalid option: {0}", UserInput);
                }

            }
        }
    }