WebClient下载后使用中的文件

Question

I've downloaded a file and tried to delete it based on its size after doing so, however, it says the file is in use.

WebClient wc = new WebClient();

wc.DownloadFileAsync(new Uri(sb.ToString()), sbFileLocation.ToString());

 if (new FileInfo(sbFileLocation.ToString()).Length == 0)
            {
                File.Delete(sbFileLocation.ToString());
            }

As you can see, File.Delete raises an exception, stating that the file is in use.

Is there some way to close it and then delete it?

Answer 1

DownloadFileAsync(Uri, String, Object)

Downloads, to a local file, the resource with the specified URI. This method does not block the calling thread.

What this means is the file may (or may not) be completely downloaded before you call File.Delete(sbFileLocation.ToString()); . This is a typical race condition and fully explains your error.

This method downloads the resource at the URI specified by in the address parameter. When the download completes successfully, the downloaded file is named fileName on the local computer. The file is downloaded asynchronously using thread resources that are automatically allocated from the thread pool. To receive notification when the file is available, add an event handler to the DownloadFileCompleted event.

You either need to use the DownloadFileCompleted event, the synchronous WebClient.DownloadFile method or await the Task based WebClient.DownloadFileTaskAsync method