ASP.NET Core memory cache

• ASP.NET Core MVC
• ASP.NET Core logging with Serilog
• ASP.NET Core managed config
• ASP.NET Core MVC with /api/-area
• ASP.NET Core API versioning
• ASP.NET Core API with Swagger UI
• ASP.NET Core EF in separate project
• ASP.NET Core AutoMapper
• ASP.NET Core response cache
• ASP.NET Core memory cache
• ASP.NET Core TypeScript

Response cache is fine for simpler operations, but sometimes you need more fine grained control. System.Runtime.Caching.MemoryCache has builtin support for in-memory cache with expiry.

Install

Install-Package System.Runtime.Caching

Implement

To register as a service add this to Startup.cs ConfigureServices:

services.AddMemoryCache();

Use

public class HomeController : Controller
{
    private readonly IMemoryCache _cache;

    public HomeController(IMemoryCache memoryCache)
    {
        _cache = memoryCache;
    }

    [HttpGet]
    public string CurrentTime()
    {
        var cacheEntry = _cache.GetOrCreate("CurrentTime", entry =>
        {
            entry.SlidingExpiration = TimeSpan.FromSeconds(10);
            return DateTime.Now.ToString();
        });

        return cacheEntry;
    }
}

A colleague requested a more complex scenario where we need the cache to update exactly every 1 minute, since numbers from all requests to that particular API should be approximately in sync.

[HttpGet]
public string CurrentTime()
{
    var cacheEntry = _cache.GetOrCreate("CurrentTime", entry =>
    {
        // Calculate next whole minute
        var now = DateTimeOffset.Now.ToUnixTimeSeconds();
        var expires = now + 60 - (now % 60);

        entry.AbsoluteExpiration = DateTimeOffset.FromUnixTimeSeconds(expires);
        return DateTime.Now.ToString();
    });

    return cacheEntry;
}