using System.Collections.Concurrent;

class ConcurrentDictionary
{
    static void Main(string[] args)
    {
        ConcurrentDictionary<int, string> dict = new ConcurrentDictionary<int, string>();
        dict.TryAdd(1, "January");   //returns true
        dict.TryAdd(2, "February");  //returns true
        dict.TryAdd(3, "March");     //returns true
        dict.TryAdd(4, "Apr");     //returns true

        string updatedValue;
        bool returnTrue = dict.TryUpdate(4, "April", "Apr"); //Returns true
        dict.TryGetValue(4, out updatedValue);
        Console.WriteLine(updatedValue); //Display "April"

        bool returnsFalse = dict.TryUpdate(4, "Apr", "Apr"); //Returns false
        dict.TryGetValue(4, out updatedValue);  //Returns "April" Old value
        Console.WriteLine(updatedValue);    //Returns "April"
    }
}