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;
}