Cache.cs

using Newtonsoft.Json;
using StackExchange.Redis;
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Linq;
using System.Web;

namespace CacheAsideDemo.Data
{
    public class Cache
    {
        private static ConnectionMultiplexer __connection;
        private static ConnectionMultiplexer Connection
        {
            get
            {
                return __connection ??
                    ( __connection = ConnectionMultiplexer.Connect( ConfigurationManager.AppSettings["RedisConnString"] ) );
            }
        }

        public T GetFromCache<T>( string key, Func<T> missCallback )
        {
            T value;
            var redis = Connection.GetDatabase();
            var serializedValue = redis.StringGet( key );

            if ( !serializedValue.IsNullOrEmpty ) // Hit!
            {
                value = JsonConvert.DeserializeObject<T>( serializedValue );
            }
            else // Miss - load from callback and store in cache with expiry time of 5 minutes
            {
                value = missCallback();
                redis.StringSet( key, JsonConvert.SerializeObject( value ), TimeSpan.FromMinutes( 5 ) );
            }
            return value;
        }

        public void InvalidateCacheEntry( string key )
        {
            var redis = Connection.GetDatabase();
            redis.KeyDelete( key );
        }
    }
}

CacheAsideProductService.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using CacheAsideDemo.Models;
using StackExchange.Redis;

namespace CacheAsideDemo.Data
{
    public class CacheAsideProductService : IProductService
    {
        private IProductService _underlyingService;
        private Cache _cache;

        public CacheAsideProductService( IProductService underlyingService, Cache cache )
        {
            _underlyingService = underlyingService;
            _cache = cache;
        }

        public Product Get( Guid id )
        {
            var cacheKey = String.Format( "Product_{0}", id );
            return _cache.GetFromCache<Product>( cacheKey, () => _underlyingService.Get( id ) );
        }

        public void Update( Guid id, Product product )
        {
            var cacheKey = String.Format( "Product_{0}", id );
            _underlyingService.Update( id, product );
            _cache.InvalidateCacheEntry( cacheKey );
        }
    }
}

ProductController-WithCaching.cs

using CacheAsideDemo.Data;
using CacheAsideDemo.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;

namespace CacheAsideDemo.Controllers
{
    [RoutePrefix( "api/products" )]
    public class ProductController : ApiController
    {
        //IProductService _service = new ProductService(); // No Caching
        IProductService _service = new CacheAsideProductService( new ProductService(), new Cache() );

        [HttpGet, Route( "{id:guid}" )]
        public Product Get( Guid id )
        {
            return _service.Get( id );
        }

        [HttpPut, Route( "{id:guid}" )]
        public Product Update( Guid id, Product product )
        {
            _service.Update( id, product );
            return product;
        }
    }
}

ProductController.cs

using CacheAsideDemo.Data;
using CacheAsideDemo.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;

namespace CacheAsideDemo.Controllers
{
    [RoutePrefix( "api/products" )]
    public class ProductController : ApiController
    {
        IProductService _service = new ProductService();

        [HttpGet, Route( "{id:guid}" )]
        public Product Get( Guid id )
        {
            return _service.Get( id );
        }

        [HttpPut, Route( "{id:guid}" )]
        public Product Update( Guid id, Product product )
        {
            _service.Update( id, product );
            return product;
        }
    }
}