使用進度條下載文件

Question

我想在方法中下載文件，然後使用第一種方法中存儲在變量中的一些數據繼續使用該文件。 我知道你可以使用DownloadFileAsync，但是我需要在DownloadFileCompleted方法中繼續我的工作，並且不能從那裏訪問變量（除非我聲明瞭一些全局變量並使用它，儘管這不是正確的方法我想）。

因此，我使用Google搜索並找到了另一種方式，通過手動下載文件，一點一點地進行。這對我來說很合適。儘管我想知道的是，如果還有其他方法/解決方案對我的問題更簡單？

或者，如果你可以用事件玩耍和實現的東西，對我更合適:)

哦，請更改我的問題，如果你找到一個更好的標題，我想不出一個的。

Answer 1

你必須一塊一塊地更新進度條。這段代碼有訣竅。

public class WebDownloader 
{ 
    private static readonly ILog log = LogManager.GetLogger(typeof(WebDownloader)); 

    public delegate void DownloadProgressDelegate(int percProgress); 

public static void Download(string uri, string localPath, DownloadProgressDelegate progressDelegate) 
    { 
     long remoteSize; 
     string fullLocalPath; // Full local path including file name if only directory was provided. 

     log.InfoFormat("Attempting to download file (Uri={0}, LocalPath={1})", uri, localPath); 

     try 
     { 
      /// Get the name of the remote file. 
      Uri remoteUri = new Uri(uri); 
      string fileName = Path.GetFileName(remoteUri.LocalPath); 

      if (Path.GetFileName(localPath).Length == 0) 
       fullLocalPath = Path.Combine(localPath, fileName); 
      else 
       fullLocalPath = localPath; 

      /// Have to get size of remote object through the webrequest as not available on remote files, 
      /// although it does work on local files. 
      using (WebResponse response = WebRequest.Create(uri).GetResponse()) 
      using (Stream stream = response.GetResponseStream()) 
       remoteSize = response.ContentLength; 

      log.InfoFormat("Downloading file (Uri={0}, Size={1}, FullLocalPath={2}).", 
       uri, remoteSize, fullLocalPath); 
     } 
     catch (Exception ex) 
     { 
      throw new ApplicationException(string.Format("Error connecting to URI (Exception={0})", ex.Message), ex); 
     } 

     int bytesRead = 0, bytesReadTotal = 0; 

     try 
     { 
      using (WebClient client = new WebClient()) 
      using (Stream streamRemote = client.OpenRead(new Uri(uri))) 
      using (Stream streamLocal = new FileStream(fullLocalPath, FileMode.Create, FileAccess.Write, FileShare.None)) 
      { 
       byte[] byteBuffer = new byte[1024 * 1024 * 2]; // 2 meg buffer although in testing only got to 10k max usage. 
       int perc = 0; 
       while ((bytesRead = streamRemote.Read(byteBuffer, 0, byteBuffer.Length)) > 0) 
       { 
        bytesReadTotal += bytesRead; 
        streamLocal.Write(byteBuffer, 0, bytesRead); 
        int newPerc = (int)((double)bytesReadTotal/(double)remoteSize * 100); 
        if (newPerc > perc) 
        { 
         log.InfoFormat("...Downloading (BytesRead={0}, Perc={1})...", bytesReadTotal, perc); 
         perc = newPerc; 
         if (progressDelegate != null) 
          progressDelegate(perc); 
        } 
       } 
      } 
     } 
     catch (Exception ex) 
     { 
      throw new ApplicationException(string.Format("Error downloading file (Exception={0})", ex.Message), ex); 
     } 

     log.InfoFormat("File successfully downloaded (Uri={0}, BytesDownloaded={1}/{2}, FullLocalPath={3}).", 
      uri, bytesReadTotal, remoteSize, fullLocalPath); 
    } 
} 

您將需要分離一個線程來運行此代碼，因爲它顯然是同步的。

例如

Task.Factory.StartNew(_ => Download(...));