etag support

Author: nzdev

src/UmbracoFileSystemProviders.Azure.Media/FileSystemVirtualFile.cs

@@ -75,6 +75,12 @@ public override Stream Open()
                 cache.SetExpires(DateTime.Now.ToUniversalTime().AddDays(maxDays));
                 cache.SetMaxAge(new TimeSpan(maxDays, 0, 0, 0));
                 cache.SetRevalidation(HttpCacheRevalidation.AllCaches);
+                cache.SetLastModified(azureBlobFileSystem.GetLastModified(VirtualPath).DateTime);
+                var etag = ((AzureBlobFileSystem)azureBlobFileSystem).FileSystem.GetETag(VirtualPath);
+                if (!string.IsNullOrWhiteSpace(etag))
+                {
+                    cache.SetETag(etag);
+                }
             }
 
             return this.stream();

src/UmbracoFileSystemProviders.Azure/AzureFileSystem.cs

@@ -704,6 +704,20 @@ public Stream OpenFile(string path)
             return null;
         }
 
+        public string GetETag(string path,string format = "G")
+        {
+            Current.Logger.Debug<AzureBlobFileSystem>($"GetSize(path) method executed with path:{path}");
+
+            var blockBlob = this.GetBlockBlobReference(path);
+
+            if (blockBlob != null)
+            {
+                var properties = blockBlob.GetProperties().Value;
+                return properties.ETag.ToString(format);
+            }
+
+            return null;
+        }
 
         private string _connectionString;