Merge pull request #137 from filipw/bugfix/118

prevent race condition in CacheOutputAttribute

Author: filipw

src/WebApi.OutputCache.V2/CacheOutputAttribute.cs

@@ -20,6 +20,7 @@ namespace WebApi.OutputCache.V2
     [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
     public class CacheOutputAttribute : ActionFilterAttribute
     {
+        private const string CurrentRequestMediaType = "CacheOutput:CurrentRequestMediaType";
         protected static MediaTypeHeaderValue DefaultMediaType = new MediaTypeHeaderValue("application/json") {CharSet = Encoding.UTF8.HeaderName};
 
         /// <summary>
@@ -62,8 +63,6 @@ public class CacheOutputAttribute : ActionFilterAttribute
         /// </summary>
         public Type CacheKeyGenerator { get; set; }
 
-        private MediaTypeHeaderValue _responseMediaType;
-        
         // cache repository
         private IApiOutputCache _webApiCache;
 
@@ -138,8 +137,9 @@ public override void OnActionExecuting(HttpActionContext actionContext)
 
             var cacheKeyGenerator = config.CacheOutputConfiguration().GetCacheKeyGenerator(actionContext.Request, CacheKeyGenerator);
 
-            _responseMediaType = GetExpectedMediaType(config, actionContext);
-            var cachekey = cacheKeyGenerator.MakeCacheKey(actionContext, _responseMediaType, ExcludeQueryStringFromCacheKey);
+            var responseMediaType = GetExpectedMediaType(config, actionContext);
+            actionContext.Request.Properties[CurrentRequestMediaType] = responseMediaType;
+            var cachekey = cacheKeyGenerator.MakeCacheKey(actionContext, responseMediaType, ExcludeQueryStringFromCacheKey);
 
             if (!_webApiCache.Contains(cachekey)) return;
 
@@ -184,10 +184,12 @@ public override async Task OnActionExecutedAsync(HttpActionExecutedContext actio
             var cacheTime = CacheTimeQuery.Execute(DateTime.Now);
             if (cacheTime.AbsoluteExpiration > DateTime.Now)
             {
-                var config = actionExecutedContext.Request.GetConfiguration().CacheOutputConfiguration();
+                var httpConfig = actionExecutedContext.Request.GetConfiguration();
+                var config = httpConfig.CacheOutputConfiguration();
                 var cacheKeyGenerator = config.GetCacheKeyGenerator(actionExecutedContext.Request, CacheKeyGenerator);
 
-                var cachekey = cacheKeyGenerator.MakeCacheKey(actionExecutedContext.ActionContext, _responseMediaType, ExcludeQueryStringFromCacheKey);
+                var responseMediaType = actionExecutedContext.Request.Properties[CurrentRequestMediaType] as MediaTypeHeaderValue ?? GetExpectedMediaType(httpConfig, actionExecutedContext.ActionContext);
+                var cachekey = cacheKeyGenerator.MakeCacheKey(actionExecutedContext.ActionContext, responseMediaType, ExcludeQueryStringFromCacheKey);
 
                 if (!string.IsNullOrWhiteSpace(cachekey) && !(_webApiCache.Contains(cachekey)))
                 {