How to print the fibonacci series provided a given limit by the user in c#?

using System;
class abc
{
    int a = 0, b = 1, limit;
    public void fun()
    {
        Console.WriteLine("Enter the limit upto which you want to print fibonacci series: ");
        limit = Convert.ToInt32(Console.ReadLine());
        Console.WriteLine("fibonacci series is : ");
        Console.WriteLine(a);
        while (b < limit)
        {
            Console.WriteLine(b);
            b = b + a;
            a = b - a;
        }
        Console.ReadKey();
    }
}
class fibonacci
{
    public static void Main(string[] args)
    {
        abc a1 = new abc();
        a1.fun();
    }
}
Output