Caching

Introduction#

Caching helps in improving performance of an application by maintaining easily accessible copy of the data. Aspnet Core comes with two easy to use and testing friendly caching abstractions.

Memory Cache will store data in to local server’s memory caching.

Distributed Cache will hold the data cache in a centralized location which is accessible by servers in cluster. It comes with three implementations out of the box : In Memory (for unit testing and local dev), Redis and Sql Server.

Using InMemory cache in ASP.NET Core application

To use an in memory cache in your ASP.NET application, add the following dependencies to your project.json file:

  "Microsoft.Extensions.Caching.Memory": "1.0.0-rc2-final",

add the cache service (from Microsoft.Extensions.Caching.Memory) to ConfigureServices method in Startup class

services.AddMemoryCache();

To add items to the cache in our application, we will use IMemoryCache which can be injected to any class (for example Controller) as shown below.

private IMemoryCache _memoryCache;
public HomeController(IMemoryCache memoryCache)
{
    _memoryCache = memoryCache;
}

Get will return the value if it exists, but otherwise returns null.

    // try to get the cached item; null if not found
    // greeting = _memoryCache.Get(cacheKey) as string;

    // alternately, TryGet returns true if the cache entry was found
    if(!_memoryCache.TryGetValue(cacheKey, out greeting))

Use the Set method to write to the cache. Set accepts the key to use to look up the value, the value to be cached, and a set of MemoryCacheEntryOptions. The MemoryCacheEntryOptions allow you to specify absolute or sliding time-based cache expiration, caching priority, callbacks, and dependencies. One of the sample below-

_memoryCache.Set(cacheKey, greeting,
                new MemoryCacheEntryOptions()
                .SetAbsoluteExpiration(TimeSpan.FromMinutes(1)));

Distributed Caching

To leverage distributed cache, you’ll have to reference one of the available implementations :

• Redis
• Sql server

For instance you’ll register Redis implemention as follows :

public void ConfigureServices(IServiceCollection services)
{
    services.AddDistributedRedisCache(options =>
    {
        options.Configuration = "ServerAdress";
        options.InstanceName = "InstanceName";
    });
}

Require IDistributedCache dependency where you need it:

public class BooksController {
    private IDistributedCache distributedCache;

    public BooksController(IDistributedCache distributedCache) {
        this.distributedCache = distributedCache;
    }

    [HttpGet]
    public async Task<Books[]> GetAllBooks() {
        var serialized = this.distributedCache.GetStringAsync($"allbooks");
        Books[] books = null;
        if (string.IsNullOrEmpty(serialized)) {
            books = await Books.FetchAllAsync();
            this.distributedCache.SetStringAsync($"allbooks", JsonConvert.SerializeObject(books));
        } else {
            books = JsonConvert.DeserializeObject<Books[]>(serialized);
        }
        return books;
    }
}