How to ask the user to input numbers only in integer?

I want to ask the user to input a number including an if statement option were if he puts letters the last question will be asked again I've tried this but seemingly it work only for strings

        Console.Write("Write a number:");
        int num = Convert.ToInt32(Console.ReadLine());

        if (!int.TryParse(age, out num))
            while(!int.TryParse(age, out num))
            {
             Console.WriteLine(...);
             // ....
            }