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[] : 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;
         }
     }