ASP.NET Web API通过ActionFilter来实现缓存

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Web;
using System.Web.Caching;
using System.Web.Http;
using System.Web.Http.Controllers;
using System.Web.Http.Filters;

namespace WebApi
{
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
    public class CacheAttribute : ActionFilterAttribute
    {
        public string AbsoluteExpiration { get; set; }
        public string SlidingExpiration { get; set; }
        public CacheItemPriority Priority { get; set; }

        public CacheAttribute()
        {
            Priority = CacheItemPriority.Normal;
        }

        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            var actionDescriptor = actionContext.ActionDescriptor as ReflectedHttpActionDescriptor;
            if (null == actionDescriptor)
            {
                base.OnActionExecuting(actionContext);
            }
            var key = new CacheKey(actionDescriptor.MethodInfo, actionContext.ActionArguments);
            var array = HttpRuntime.Cache.Get(key.ToString()) as object[];
            if (null == array)
            {
                base.OnActionExecuting(actionContext);
                return;
            }
            var value = array.Any() ? array[0] : null;
            var actionResult = value as IHttpActionResult;
            if (null != actionResult)
            {
                actionContext.Response = actionResult.ExecuteAsync(CancellationToken.None).Result;
                return;
            }
            actionContext.Response = actionDescriptor.ResultConverter.Convert(actionContext.ControllerContext, value);
        }
    }

    public class CacheableActionDescriptor : ReflectedHttpActionDescriptor
    {
        private CacheAttribute CacheAttribute { get; }

        public CacheableActionDescriptor(ReflectedHttpActionDescriptor actionDescriptor, CacheAttribute cacheAttribute) : base(actionDescriptor.ControllerDescriptor, actionDescriptor.MethodInfo)
        {
            CacheAttribute = cacheAttribute;
        }

        public override Task<object> ExecuteAsync(HttpControllerContext controllerContext, IDictionary<string, object> arguments, CancellationToken cancellationToken)
        {  
            var absoluteExpiration = Cache.NoAbsoluteExpiration;
            var slidingExpiration = Cache.NoSlidingExpiration;
            var priority = CacheAttribute.Priority;
            if (!string.IsNullOrWhiteSpace(CacheAttribute.AbsoluteExpiration))
            {
                absoluteExpiration = DateTime.Now + TimeSpan.Parse(CacheAttribute.AbsoluteExpiration);
            }
            if (!string.IsNullOrWhiteSpace(CacheAttribute.SlidingExpiration))
            {
                slidingExpiration = TimeSpan.Parse(CacheAttribute.SlidingExpiration);
            }
            var cacheKey = new CacheKey(MethodInfo, arguments);
            var result = base.ExecuteAsync(controllerContext, arguments, cancellationToken).Result;
            HttpRuntime.Cache.Insert(cacheKey.ToString(), new[] {result}, null, absoluteExpiration, slidingExpiration, priority, null);
            return Task.FromResult(result);
        }
    }

    public class CacheableActionSelector : ApiControllerActionSelector
    {
        public override HttpActionDescriptor SelectAction(HttpControllerContext controllerContext)
        {
            var actionDescriptor = base.SelectAction(controllerContext);
            var reflectedActionDescriptor = actionDescriptor as ReflectedHttpActionDescriptor;
            if (null == reflectedActionDescriptor)
            {
                return actionDescriptor;
            }
            var cacheAttribute = reflectedActionDescriptor.GetCustomAttributes<CacheAttribute>().FirstOrDefault() ??
                                 reflectedActionDescriptor.ControllerDescriptor.GetCustomAttributes<CacheAttribute>().FirstOrDefault();
            if (null == cacheAttribute)
            {
                return actionDescriptor;
            }
            return new CacheableActionDescriptor(reflectedActionDescriptor, cacheAttribute);
        }
    }
}

注册ActionSelector

using System;
using System.Web;
using System.Web.Http;
using System.Web.Http.Controllers;
using WebApi;

namespace WebHost
{
    public class Global : HttpApplication
    {
        protected void Application_Start(object sender, EventArgs e)
        {
            // 注册ASP.NET Web API路由
            GlobalConfiguration.Configuration.Routes.MapHttpRoute("default", "api/{controller}/{id}", new { id = RouteParameter.Optional });


            // 注册CacheableActionSelector
            GlobalConfiguration.Configuration.Services.Replace(typeof(IHttpActionSelector), new CacheableActionSelector());
        }
    }
}

使用CacheAttribute

    public class DemoController : ApiController
    {
        [Cache(AbsoluteExpiration = "00:00:02", SlidingExpiration = "", Priority = CacheItemPriority.High)]
        public DateTime Get()
        {
            return DateTime.Now;
        }
    }