获取远程文件的上次修改日期

Question

I have an app with which at startup it downloads a file from a remote location (through the net) and parses it's contents.

I am trying to speed up the process of startup as the bigger the file gets the slower the app starts.

As a way to speed up the process I thought of getting the last modified date of the file and if it is newer from the file on the user's pc then and only then download it. I have found many ways to do it online but none of them are in C# (for windows store apps). Does anybody here know of a way of doing this without the need to download the file? If I am to download the file then the process is sped up at all.

My C# code for downloading the file currently is this

const string fileLocation = "link to dropbox";
            var uri = new Uri(fileLocation);
            var downloader = new BackgroundDownloader();
            StorageFile file = await ApplicationData.Current.LocalFolder.CreateFileAsync("feedlist.txt",CreationCollisionOption.ReplaceExisting);
            DownloadOperation download = downloader.CreateDownload(uri, file); 
            await download.StartAsync();

If it helps the file is stored in dropbox but if any of you guys have a suggestion for another free file hosting service I am open to suggestions

Answer 1

Generally, you can check the file time by sending HEAD request and parsing/looking HTTP header response for a Last-Modified filed. The remote server should support it and DropBox does not support this feature for direct links (only via API). But DropBox have another feature, the headers have the etag field. You should store it and check in the next request. If it changed - the file has been changed too. You can use this tool to check the remote file headers.