How do I use the tryParse method in my program?

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C#

I wrote this program and asks a user to guess a number between 20 and 30 and to avoid the user entering something like a letter, I used a certain code but I would like to know how to use the tryParse method. Could someone please put the tryParse method in my code?

using System;

class ApplicationEntry
{
    static void Main(string[] args)
    {
        bool repeat = true, repeat2 = true, repeat3 = true;
        while (repeat == true)
        {
            repeat2 = true;
            Random r = new Random();
            int numb = (r.Next(20, 30));
            while (repeat2 == true)
            {
                Console.WriteLine("Please enter a numbers between 20 and 30");
                int guess1 = Convert.ToInt32(Console.ReadLine());

                if ((guess1 < 20 || guess1 > 30) && guess1 != numb)
                {
                    Console.WriteLine("Invalid. Please enter a number between 20 and 30");
                    repeat3 = false;
                }
                else if (guess1 == numb)
                {
                    Console.WriteLine("Good job");
                    repeat2 = false;
                    repeat3 = true;
                }
                else
                {
                    Console.WriteLine("Wrong! Try again");
                    repeat2 = true;
                    repeat3 = false;
                }
                while (repeat3 == true)
                {
                    Console.WriteLine("Would you like to play again?");
                    string answer = Console.ReadLine();
                    if (answer == "yes" || answer == "Yes" || answer == "YES")
                    {
                        repeat3 = false;
                        repeat = true;
                        repeat2 = false;
                    }
                    else if (answer == "no" || answer == "No" || answer == "NO")
                    {
                        repeat = false;
                        repeat3 = false;
                    }
                    else
                    {
                        Console.WriteLine("I didn't understand that");
                    }
                    

                 }

             }
          }

            Console.Write("\nPress any key to exit program: ");
            Console.ReadKey();
     } 

}