CopyMediaExtensions.cs

public static class IMediaServiceExtensions {

        private const string UmbFile = "umbracoFile";

        public static IMedia Copy(this IMediaService mediaService, IMedia media, IMedia newLocation, string newName = "") {
            var properNewName = string.IsNullOrEmpty(newName) ? media.Name : newName;
            var newMedia = (newLocation == null) ? mediaService.CreateMedia(properNewName, -1, media.ContentType.Alias)
                                                 : mediaService.CreateMedia(properNewName, newLocation, media.ContentType.Alias);

            if (media.HasProperty(UmbFile)) {
                // We need to call save here to get a media object ID to then put in the file path.
                mediaService.Save(newMedia);

                var fileSystem = FileSystemProviderManager.Current.GetUnderlyingFileSystemProvider("media");
                var oldFilePath = media.GetValue<string>(UmbFile);    
                
                var newFilePath = Regex.Replace(oldFilePath, @"/\d{4,}/", string.Concat(Path.DirectorySeparatorChar, newMedia.Id.ToString(), Path.DirectorySeparatorChar));

                // Next, retrieve the file if it exists, and clone it using the FSProvider
                if (fileSystem.FileExists(oldFilePath)) {
                    using (var fs = fileSystem.OpenFile(oldFilePath)) {
                        fileSystem.AddFile(newFilePath, fs, false);
                        newMedia.Properties[UmbFile].Value = newFilePath;
                    }
                }
            }

            foreach (var prop in media.Properties.Where(p => p.Alias != UmbFile)) {
                newMedia.Properties[prop.Alias].Value = prop.Value;
            }

            mediaService.Save(newMedia);

            if (media.Children().Any()) {
                foreach (var child in media.Children()) {
                    mediaService.Copy(child, newMedia);
                }
            }

            return newMedia;
        }

        public static IMedia Copy(this IMediaService mediaService, IMedia media, int newLocationId, string newName = "") {
            return mediaService.Copy(media, mediaService.GetById(newLocationId), newName);
        }
    }