is their any way to loop an if statement if it does not meet a specific requirement

        Console.WriteLine("ALL WORDS YOU TYPE MUST BE LOWERCASE UNLESS STATED OTHERWISE, DO 
        YOU UNDERSTAND? \n \n YES | NO \n");
        string answer = "undefined";

        userInput();
        answer = Console.ReadLine();
        userInputDone();


        if (answer == "yes")
        {
            Console.ForegroundColor = ConsoleColor.Green;
            Console.WriteLine("\nGreat :)\n");
            Console.ForegroundColor = ConsoleColor.Gray;
        } 
        else if (answer == "no")
        {
            Console.ForegroundColor = ConsoleColor.Red;
            Console.WriteLine("\nTOO BAD\n");
            Console.ForegroundColor = ConsoleColor.Gray;
        }


        Console.WriteLine("What would you lke to do? \n \n PLAY | INSTRUCTIONS");

I'm working on a text-based game to get used to C#, how would i go about looping the if statement so that if the user does not type in yes or no it writes "invalid input, try again" and restarts from the first "Console.WriteLine()"