using System;

using Microsoft.Extensions.Caching.Memory;

public class Program

{

    public static void Main()

    {

        IMemoryCache cache = new MemoryCache(new MemoryCacheOptions());

        object key = new object();

        Console.WriteLine("{0}", cache.TryGetValue(key, out int val)?val:"key not found");

        Incr(key, cache);

        Console.WriteLine(cache.Get(key));

        Incr(key, cache);

        Console.WriteLine(cache.Get(key));

    }

    public static void Incr(object key, IMemoryCache cache)

    {

        int currentValue = cache.GetOrCreate(key, _ => 0);

        cache.Set(key, currentValue+1);

    }

}