Post processing event is now awaitable

Former-commit-id: 79488db462d8d721315b20fffc379f14d3dbf5fd

src/ImageProcessor.Web/Caching/CacheIndexer.cs

@@ -41,7 +41,7 @@ namespace ImageProcessor.Web.Caching
 
             if (cachedImage == null)
             {
-                cachedImage = await TaskHelpers.Run(() => GetCachedImage(cachedPath));
+                cachedImage = await Task.Run(() => GetCachedImage(cachedPath));
 
                 if (cachedImage != null)
                 {

src/ImageProcessor.Web/Caching/DiskCache.cs

@@ -193,7 +193,7 @@ namespace ImageProcessor.Web.Caching
         /// </returns>
         internal async Task TrimCachedFolderAsync(string path)
         {
-            await TaskHelpers.Run(() => this.TrimCachedFolders(path));
+            await Task.Run(() => this.TrimCachedFolders(path));
         }
         #endregion
 

src/ImageProcessor.Web/Helpers/TaskHelpers.cs

@@ -1,51 +0,0 @@
-// --------------------------------------------------------------------------------------------------------------------
-// <copyright file="TaskHelpers.cs" company="James South">
-//   Copyright (c) James South.
-//   Licensed under the Apache License, Version 2.0.
-// </copyright>
-// <summary>
-//   Provides some syntactic sugar to run tasks.
-// </summary>
-// --------------------------------------------------------------------------------------------------------------------
-
-namespace ImageProcessor.Web.Helpers
-{
-    #region Using
-    using System;
-    using System.Threading.Tasks;
-    #endregion
-
-    /// <summary>
-    /// Provides some syntactic sugar to run tasks.
-    /// </summary>
-    public sealed class TaskHelpers
-    {
-        /// <summary>
-        /// Queues the specified work to run on the ThreadPool and returns a Task handle for that work.
-        /// </summary>
-        /// <param name="action">The work to execute asynchronously</param> 
-        /// <returns>A Task that represents the work queued to execute in the ThreadPool.</returns>
-        /// <exception cref="T:System.ArgumentNullException"> 
-        /// The <paramref name="action"/> parameter was null. 
-        /// </exception>
-        public static Task Run(Action action)
-        {
-            return Task.Factory.StartNew(action);
-        }
-
-        /// <summary> 
-        /// Queues the specified work to run on the ThreadPool and returns a proxy for the 
-        /// Task(TResult) returned by <paramref name="function"/>.
-        /// </summary> 
-        /// <typeparam name="TResult">The type of the result returned by the proxy Task.</typeparam>
-        /// <param name="function">The work to execute asynchronously</param>
-        /// <returns>A Task(TResult) that represents a proxy for the Task(TResult) returned by <paramref name="function"/>.</returns>
-        /// <exception cref="T:System.ArgumentNullException"> 
-        /// The <paramref name="function"/> parameter was null.
-        /// </exception> 
-        public static Task<TResult> Run<TResult>(Func<TResult> function)
-        {
-            return Task<TResult>.Factory.StartNew(function);
-        }
-    }
-}

src/ImageProcessor.Web/HttpModules/ImageProcessingModule.cs

@@ -44,6 +44,11 @@ namespace ImageProcessor.Web.HttpModules
         /// </summary>
         private const string CachedResponseTypeKey = "CACHED_IMAGE_RESPONSE_TYPE_054F217C-11CF-49FF-8D2F-698E8E6EB58F";
 
+        /// <summary>
+        /// The key for storing the cached path of the current image.
+        /// </summary>
+        private const string CachedPathKey = "CACHED_IMAGE_PATH_TYPE_E0741478-C17B-433D-96A8-6CDA797644E9";
+
         /// <summary>
         /// The key for storing the file dependency of the current image.
         /// </summary>
@@ -134,8 +139,12 @@ namespace ImageProcessor.Web.HttpModules
                 preserveExifMetaData = ImageProcessorConfiguration.Instance.PreserveExifMetaData;
             }
 
-            EventHandlerTaskAsyncHelper wrapper = new EventHandlerTaskAsyncHelper(this.PostAuthorizeRequest);
-            context.AddOnPostAuthorizeRequestAsync(wrapper.BeginEventHandler, wrapper.EndEventHandler);
+            EventHandlerTaskAsyncHelper postAuthorizeHelper = new EventHandlerTaskAsyncHelper(this.PostAuthorizeRequest);
+            context.AddOnPostAuthorizeRequestAsync(postAuthorizeHelper.BeginEventHandler, postAuthorizeHelper.EndEventHandler);
+
+            EventHandlerTaskAsyncHelper postProcessHelper = new EventHandlerTaskAsyncHelper(this.PostProcessImage);
+            context.AddOnPostRequestHandlerExecuteAsync(postProcessHelper.BeginEventHandler, postProcessHelper.EndEventHandler);
+
             context.PreSendRequestHeaders += this.ContextPreSendRequestHeaders;
         }
 
@@ -195,6 +204,39 @@ namespace ImageProcessor.Web.HttpModules
             return this.ProcessImageAsync(context);
         }
 
+        /// <summary>
+        /// Occurs when the ASP.NET event handler finishes execution.
+        /// </summary>
+        /// <param name="sender">
+        /// The source of the event.
+        /// </param>
+        /// <param name="e">
+        /// An <see cref="T:System.EventArgs">EventArgs</see> that contains the event data.
+        /// </param>
+        /// <returns>
+        /// The <see cref="T:System.Threading.Tasks.Task"/>.
+        /// </returns>
+        private Task PostProcessImage(object sender, EventArgs e)
+        {
+            HttpContext context = ((HttpApplication)sender).Context;
+            object cachedPathObject = context.Items[CachedPathKey];
+
+            if (cachedPathObject != null)
+            {
+                string cachedPath = cachedPathObject.ToString();
+
+                // Fire the post processing event.
+                EventHandler<PostProcessingEventArgs> handler = OnPostProcessing;
+                if (handler != null)
+                {
+                    context.Items[CachedPathKey] = null;
+                    return Task.Run(() => handler(this, new PostProcessingEventArgs { CachedImagePath = cachedPath }));
+                }
+            }
+
+            return Task.FromResult<object>(null);
+        }
+
         /// <summary>
         /// Occurs just before ASP.NET send HttpHeaders to the client.
         /// </summary>
@@ -386,14 +428,8 @@ namespace ImageProcessor.Web.HttpModules
                                                     // Trim the cache.
                                                     await cache.TrimCachedFolderAsync(cachedPath);
 
-                                                    // Fire the post processing event.
-                                                    EventHandler<PostProcessingEventArgs> handler = OnPostProcessing;
-                                                    if (handler != null)
-                                                    {
-                                                        handler.Invoke(this, new PostProcessingEventArgs() { CachedImagePath = cachedPath });
-                                                    }
-
-                                                    // Store the response type and cache dependency in the context for later retrieval.
+                                                    // Store the cached path, response type, and cache dependency in the context for later retrieval.
+                                                    context.Items[CachedPathKey] = cachedPath;
                                                     context.Items[CachedResponseTypeKey] = imageFactory.CurrentImageFormat.MimeType;
                                                     context.Items[CachedResponseFileDependency] = new List<string> { cachedPath };
                                                 }
@@ -426,14 +462,8 @@ namespace ImageProcessor.Web.HttpModules
                                     // Trim the cache.
                                     await cache.TrimCachedFolderAsync(cachedPath);
 
-                                    // Fire the post processing event.
-                                    EventHandler<PostProcessingEventArgs> handler = OnPostProcessing;
-                                    if (handler != null)
-                                    {
-                                        handler.Invoke(this, new PostProcessingEventArgs() { CachedImagePath = cachedPath });
-                                    }
-
-                                    // Store the response type and cache dependencies in the context for later retrieval.
+                                    // Store the cached path, response type, and cache dependencies in the context for later retrieval.
+                                    context.Items[CachedPathKey] = cachedPath;
                                     context.Items[CachedResponseTypeKey] = imageFactory.CurrentImageFormat.MimeType;
                                     context.Items[CachedResponseFileDependency] = new List<string> { requestPath, cachedPath };
                                 }

src/ImageProcessor.Web/ImageProcessor.Web.csproj

@@ -62,7 +62,6 @@
     <Compile Include="Helpers\ResourceHelpers.cs" />
     <Compile Include="Helpers\ImageHelpers.cs" />
     <Compile Include="Helpers\RemoteFile.cs" />
-    <Compile Include="Helpers\TaskHelpers.cs" />
     <Compile Include="HttpModules\ImageProcessingModule.cs" />
     <Compile Include="ImageFactoryExtensions.cs" />
     <Compile Include="Processors\Alpha.cs" />

src/TestWebsites/MVC/Global.asax.cs

@@ -9,7 +9,9 @@ using System.Web.Routing;
 namespace Test_Website_NET45
 {
     using System.Diagnostics;
+    using System.Threading.Tasks;
 
+    using ImageProcessor.Web.Helpers;
     using ImageProcessor.Web.HttpModules;
 
     // Note: For instructions on enabling IIS6 or IIS7 classic mode, 
@@ -26,6 +28,12 @@ namespace Test_Website_NET45
 
             // Test the post processing event.
             ImageProcessingModule.OnPostProcessing += (sender, args) => Debug.WriteLine(args.CachedImagePath);
+            //ImageProcessingModule.OnPostProcessing += this.WritePath;
+        }
+
+        private async void WritePath(object sender, PostProcessingEventArgs e)
+        {
+            await Task.Run(() => Debug.WriteLine(e.CachedImagePath));
         }
     }
 }

src/TestWebsites/MVC/Web.config

@@ -28,7 +28,7 @@
   <system.web>
 
     <httpRuntime targetFramework="4.5" />
-
+    <customErrors mode="Off"/>
     <compilation debug="true" targetFramework="4.5" />
 
     <pages>