Force an user to pick a valid option c#

Question

How can I make an user chose a valid option to run the code and ask to re-input the value if he doesn't in let's say... an if statement? example
class Car{
public String color;
}
class Ford:Car{
public Ford();
color = "red";
}
class Renault:Car{
public Renault();
color = blue;
{
Car MyNewCar; //undefined object
int x;
x = Convert.ToInt32(Console.ReadLine());
if (x == 1){
Car MyNewCar = Ford;
}
else if (x==2) {
Car MyNewCar = new Renault;
}
how do I force them to pick a number again if they don't put 1 or 2?

Answer 1

Tell me if something is not clear, I omitted the writeline parts so it would fit in the character limits. that's a code I just made for the question btw it's probabbly wrong but I hope you get what I'm asking

Answer 2

Use a while loop.

While input is not 1 or 2, prompt for input.