fix bug for cache vary scenarios

Author: lanlanlee2008

src/OutputCacheModuleAsync/InMemoryOutputCacheProvider.cs

@@ -30,8 +30,8 @@ public override object Get(string key) {
         }
 
         public override object Add(string key, object entry, DateTime utcExpiry) {
-            DateTimeOffset expiration = (utcExpiry == Cache.NoAbsoluteExpiration) ? ObjectCache.InfiniteAbsoluteExpiration : utcExpiry;           
-            return _cache.Add(key, entry, expiration) ? entry : null;
+            DateTimeOffset expiration = (utcExpiry == Cache.NoAbsoluteExpiration) ? ObjectCache.InfiniteAbsoluteExpiration : utcExpiry;
+            return _cache.AddOrGetExisting(key, entry, expiration);
         }
 
         public override void Set(string key, object entry, DateTime utcExpiry) {

src/OutputCacheModuleAsync/OutputCacheHelper.cs

@@ -294,7 +294,7 @@ public bool IsAcceptableEncoding(string contentEncoding, string acceptEncoding)
             }
             double weight = GetAcceptableEncodingHelper(contentEncoding, acceptEncoding);
             return !(weight == 0) &&
-                   (!(weight <= 0) || GetAcceptableEncodingHelper(Asterisk, acceptEncoding) == 0);
+                   (!(weight <= 0) || GetAcceptableEncodingHelper(Asterisk, acceptEncoding) != 0);
         }
 
         public bool IsResponseCacheable() {
@@ -509,7 +509,7 @@ private bool HasDependencyChanged(string depKey, string[] fileDeps, string kerne
                     DependencyCacheTimeSpan = Cache.NoSlidingExpiration,
                     DependencyRemovedCallback = null
                 };
-                memoryCache.Add(depKey, dcew, DateTimeOffset.MaxValue);
+                memoryCache.Set(depKey, dcew, DateTimeOffset.MaxValue);
                 return false;
             }
             // file dependencies have changed
@@ -596,24 +596,22 @@ private async Task InsertResponseAsync(string cachedVaryKey,
                 string depKey = OutputcacheKeyprefixDependencies + dependencies.GetUniqueID();
                 OutputCacheEntry oce = Convert(rawResponse, depKey, dependencies.GetFileDependencies());
                 await provider.SetAsync(rawResponseKey, oce, absExp);
-                {
-                    // use Add and dispose dependencies if there's already one in the cache
-                    var dce = new DependencyCacheEntry {
-                        RawResponseKey = rawResponseKey,
-                        KernelCacheUrl = oce.KernelCacheUrl,
-                        Name = provider.Name
-                    };
-                    var dcew = new DependencyCacheEntryWrapper {
-                        DependencyCacheEntry = dce,
-                        Dependencies = dependencies,
-                        CacheItemPriority = System.Web.Caching.CacheItemPriority.Normal,
-                        DependencyCacheTimeSpan = Cache.NoSlidingExpiration,
-                        DependencyRemovedCallback = null
-                    };
-                    object d = await provider.AddAsync(depKey, dcew, absExp);
-                    if (d != null) {
-                        dependencies.Dispose();
-                    }
+                // use Add and dispose dependencies if there's already one in the cache
+                var dce = new DependencyCacheEntry {
+                    RawResponseKey = rawResponseKey,
+                    KernelCacheUrl = oce.KernelCacheUrl,
+                    Name = provider.Name
+                };
+                var dcew = new DependencyCacheEntryWrapper {
+                    DependencyCacheEntry = dce,
+                    Dependencies = dependencies,
+                    CacheItemPriority = System.Web.Caching.CacheItemPriority.Normal,
+                    DependencyCacheTimeSpan = Cache.NoSlidingExpiration,
+                    DependencyRemovedCallback = null
+                };
+                object d = await provider.AddAsync(depKey, dcew, absExp);
+                if (d != null) {
+                    dependencies.Dispose();
                 }
             }
         }

src/OutputCacheModuleAsync/OutputCacheModuleAsync.cs

@@ -60,16 +60,15 @@ private async Task OnEnterAsync(object source, EventArgs eventArgs) {
             //  - a CachedVary object (if the object varies by something)
             //  - a CachedRawResponse object (i.e. it doesn't vary on anything)
             //  First assume it's a CacheVary and try to get the cachedItem with it
-            CachedRawResponse cachedRawResponse;
+            CachedRawResponse cachedRawResponse = null;
             var cachedVary = item as CachedVary;
             if (cachedVary != null) {
                 var cachedItem = await helper.GetAsCacheVaryAsync(cachedVary);
-                if (cachedItem == null) {
-                    return;
+                if (cachedItem != null) {
+                    cachedRawResponse = (CachedRawResponse)cachedItem;
                 }
-                 cachedRawResponse = (CachedRawResponse)cachedItem;
             }
-            else {
+            if(cachedRawResponse == null) {
                 cachedRawResponse = item as CachedRawResponse;
             }
             if (cachedRawResponse == null) {