Another attempt at fixing: U4-4049 Some images fail when uploading multiple media files

src/Umbraco.Web/Editors/MediaController.cs

@@ -331,7 +331,7 @@ namespace Umbraco.Web.Editors
             }
         }
 
-        [EnsureUserPermissionForMedia("folder.ParentId")]
+        [EnsureUserPermissionForMedia("folder.ParentId")]        
         public MediaItemDisplay PostAddFolder(EntityBasic folder)
         {
             var mediaService = ApplicationContext.Services.MediaService;
@@ -347,8 +347,8 @@ namespace Umbraco.Web.Editors
         /// <returns></returns>
         /// <remarks>
         /// We cannot validate this request with attributes (nicely) due to the nature of the multi-part for data.
-        /// 
         /// </remarks>
+        [FileUploadCleanupFilter(false)]
         public async Task<HttpResponseMessage> PostAddFile()
         {
             if (Request.Content.IsMimeMultipartContent() == false)
@@ -387,7 +387,7 @@ namespace Umbraco.Web.Editors
                 return Request.CreateResponse(HttpStatusCode.Unauthorized);
             }
 
-            var tempFiles = new List<string>();
+            var tempFiles = new PostedFiles();
 
             //get the files
             foreach (var file in result.FileData)
@@ -416,19 +416,29 @@ namespace Umbraco.Web.Editors
                     LogHelper.Warn<MediaController>("Cannot upload file " + file + ", it is not an approved file type");
                 }
 
-                tempFiles.Add(file.LocalFileName);
+                tempFiles.UploadedFiles.Add(new ContentItemFile
+                {
+                    FileName = fileName,
+                    PropertyAlias = Constants.Conventions.Media.File,
+                    TempFilePath = file.LocalFileName
+                });
             }
 
-            //now we can remove the temp files
-            foreach (var tempFile in tempFiles)
-            {
-                System.IO.File.Delete(tempFile);    
-            }
-            
-
-            return Request.CreateResponse(HttpStatusCode.OK);
+            return Request.CreateResponse(HttpStatusCode.OK, tempFiles);
         }
 
+        /// <summary>
+        /// This is used for the response of PostAddFile so that we can analyze the response in a filter and remove the 
+        /// temporary files that were created.
+        /// </summary>
+        private class PostedFiles : IHaveUploadedFiles
+        {
+            public PostedFiles()
+            {
+                UploadedFiles = new List<ContentItemFile>();
+            }
+            public List<ContentItemFile> UploadedFiles { get; private set; }
+        }
 
         /// <summary>
         /// Ensures the item can be moved/copied to the new location

src/Umbraco.Web/WebApi/Filters/FileUploadCleanupFilterAttribute.cs

@@ -1,4 +1,5 @@
 using System.Linq;
+using System.Net.Http;
 using System.Web.Http.Filters;
 using Umbraco.Core.Models;
 using Umbraco.Web.Models.ContentEditing;
@@ -11,6 +12,17 @@ namespace Umbraco.Web.WebApi.Filters
     /// </summary>
     internal sealed class FileUploadCleanupFilterAttribute : ActionFilterAttribute
     {
+        private readonly bool _incomingModel;
+
+        /// <summary>
+        /// Constructor specifies if the filter should analyze the incoming or outgoing model
+        /// </summary>
+        /// <param name="incomingModel"></param>
+        public FileUploadCleanupFilterAttribute(bool incomingModel = true)
+        {
+            _incomingModel = incomingModel;
+        }
+
         /// <summary>
         /// Returns true so that other filters can execute along with this one
         /// </summary>
@@ -23,18 +35,40 @@ namespace Umbraco.Web.WebApi.Filters
         {
             base.OnActionExecuted(actionExecutedContext);
 
-            if (actionExecutedContext.ActionContext.ActionArguments.Any())
+            if (_incomingModel)
             {
-                var contentItem = actionExecutedContext.ActionContext.ActionArguments.First().Value as IHaveUploadedFiles;   
-                if (contentItem != null)
+                if (actionExecutedContext.ActionContext.ActionArguments.Any())
                 {
-                    //cleanup any files associated
-                    foreach (var f in contentItem.UploadedFiles)
+                    var contentItem = actionExecutedContext.ActionContext.ActionArguments.First().Value as IHaveUploadedFiles;
+                    if (contentItem != null)
                     {
-                        File.Delete(f.TempFilePath);
+                        //cleanup any files associated
+                        foreach (var f in contentItem.UploadedFiles)
+                        {
+                            File.Delete(f.TempFilePath);
+                        }
                     }
                 }
             }
+            else
+            {
+                var objectContent = actionExecutedContext.Response.Content as ObjectContent;
+                if (objectContent != null)
+                {
+                    var uploadedFiles = objectContent.Value as IHaveUploadedFiles;
+                    if (uploadedFiles != null)
+                    {
+                        //cleanup any files associated
+                        foreach (var f in uploadedFiles.UploadedFiles)
+                        {
+                            File.Delete(f.TempFilePath);
+                            //clear out the temp path so it's not returned in the response
+                            f.TempFilePath = "";
+                        }
+                    }
+                }
+            }
+            
         }
     }
 }