How to use MemoryCache in C# Core Console app?

Question

I would like to use the Microsoft.Extensions.Caching.Memory.MemoryCache in a .NET Core 2.0 console app (Actually, in a library that is either used in a console or in a asp.net app)

I've created a test app:

using System;

namespace ConsoleTest
{
    class Program
    {
        static void Main(string[] args)
        {
            var cache = new Microsoft.Extensions.Caching.Memory.MemoryCache(new Microsoft.Extensions.Caching.Memory.MemoryCacheOptions());

            int count = cache.Count;
            cache.CreateEntry("item1").Value = 1;
            int count2 = cache.Count;
            cache.TryGetValue("item1", out object item1);
            int count3 = cache.Count;
            cache.TryGetValue("item2", out object item2);
            int count4 = cache.Count;

            Console.WriteLine("Hello World!");
        }
    }
}

Unfortunately, this is not working. The items are not added to the cache and they can not be retrieved.

I suspect I need to use DependencyInjection, doing something like this:

using System;
using Microsoft.Extensions.DependencyInjection;

namespace ConsoleTest
{
    class Program
    {
        static void Main(string[] args)
        {
            var provider = new Microsoft.Extensions.DependencyInjection.ServiceCollection()
                .AddMemoryCache()
                .BuildServiceProvider();

            //And now?

            var cache = new Microsoft.Extensions.Caching.Memory.MemoryCache(new Microsoft.Extensions.Caching.Memory.MemoryCacheOptions());

            var xxx = PSP.Helpers.DependencyInjection.ServiceProvider;
            int count = cache.Count;
            cache.CreateEntry("item1").Value = 1;
            int count2 = cache.Count;
            cache.TryGetValue("item1", out object item1);
            int count3 = cache.Count;
            cache.TryGetValue("item2", out object item2);
            int count4 = cache.Count;

            Console.WriteLine("Hello World!");
        }
    }
}

Unfortunately, this is also not working, I suspect I shouldn't create a new memory cache, but get it from the service provider, but haven't been able to do that.

Any ideas?

Answer 1

After configuring the provider retrieve the cache via the GetService extension method

var provider = new ServiceCollection()
                       .AddMemoryCache()
                       .BuildServiceProvider();

//And now?
var cache = provider.GetService<IMemoryCache>();

//...other code removed for brevity;

From comments:

It's not needed to use dependency injection, the only thing needed was disposing the return value of CreateEntry(). The entry returned by CreateEntry needs to be disposed. On dispose, it is added to the cache:

using (var entry = cache.CreateEntry("item2")) { 
    entry.Value = 2; 
    entry.AbsoluteExpiration = DateTime.UtcNow.AddDays(1); 
}

Answer 2

IMemoryCache cache = new MemoryCache(new MemoryCacheOptions());
object result = cache.Set("Key", new object());
bool found = cache.TryGetValue("Key", out result);

See full Memory Cache Sample in GitHub.

You need to add NuGet Microsoft.Extensions.Caching.Memory packages in your project for use MemoryCache