The following will compile, but the code has semantic issues:
If you enter age of 19, or 13 it will loop forever. Inputs 14,15,16,17,18 will print nothing. I don't think you want to use while. Probably you want something like
if (age >=14 and age <= 19) Console.WriteLine("You are a teenager");
using System;
namespace B13
{
class Program
{
static void Main(string[] args)
{
int age = 1;
while (age >= 50)
{
Console.WriteLine("Enter your age");
age = Convert.ToInt32(Console.ReadLine());
{
if (age > 29)
{
Console.WriteLine("You are old!");
}
else
{
if (age == 19) while (age != 30) Console.WriteLine("You are getting old");
else
{
if (age == 13) while (age != 19) Console.WriteLine("You are a teenager");
else
{
if (age < 13) Console.WriteLine("You are a child");
}
Console.WriteLine(age);
Console.ReadKey();
}
}
}
}
}
}
}