Keep Coding

This question already has an answer here:
Why is the console window closing immediately without displaying my output?
18 answers
Please help! I ran this program and entered all 3 inputs but the last writeline code wouldn't run and the program just exits itself! I have no idea because I follow the book exactly!
string userName = "";
int userAge = 0;
int currentYear = 0;
Console.Write("Please enter your name: ");
userName = Console.ReadLine();
Console.Write("Please enter your age: ");
userAge = Convert.ToInt32(Console.ReadLine());
Console.Write("Please enter the current year: ");
currentYear = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("Hello World! My name is {0} and I am {1} years old. I was born in {2}.", userName, userAge, currentYear - userAge);

at the end of the code add:
Console.ReadLine();