VB.NET的HttpWebRequest在塊

Question

我正在尋找一個幫助，下面的下載文件：

在我的Windows窗體應用程序，我下載我位於控制遠程服務器上的文件。我下面的代碼：

Public Shared Function DownloadFileWithPOST(ByVal httpPath As String, ByVal storePath As String, postdata As String) As String 
    Try 
     Dim theResponse As HttpWebResponse 
     Dim theRequest As HttpWebRequest 
     Dim postdatabytes As Byte() 

     theRequest = HttpWebRequest.Create(httpPath) 


     If My.Settings.ProxyURL <> "" Then 
      Dim prx As New WebProxy(My.Settings.ProxyURL) 
      theRequest.Proxy = prx 
     End If 


     ' theRequest.Timeout = My.Settings.RequestTimeout 

     postdatabytes = System.Text.Encoding.UTF8.GetBytes(postdata) 
     theRequest.Method = "POST" 
     theRequest.ContentType = "application/x-www-form-urlencoded" 
     theRequest.ContentLength = postdatabytes.Length 

     Using stream = theRequest.GetRequestStream() 
      stream.Write(postdatabytes, 0, postdatabytes.Length) 
     End Using 



     theResponse = theRequest.GetResponse 


     Dim length As Double = theResponse.ContentLength 




     Dim writeStream As New IO.FileStream(storePath, IO.FileMode.Create) 


     Dim nRead As Integer 

     Dim readBytes(4095) As Byte 
     Dim bytesread As Integer = theResponse.GetResponseStream.Read(readBytes, 0, 4096) 



     Do Until bytesread = 0 



      'speedtimer.Start() 


      nRead += bytesread 



      writeStream.Write(readBytes, 0, bytesread) 


      bytesread = theResponse.GetResponseStream.Read(readBytes, 0, 4096) 
     Loop 

     'Close the streams 
     theResponse.GetResponseStream.Close() 
     writeStream.Close() 


     Return "OK" 
    Catch ex As Exception 
     Return ex.Message 
    End Try 
End Function 

的問題是，我們正在超時異常，如果下載未在規定時間（帶超時設置的註釋行）完成。如果下載被分塊，我會看到驅動器上的文件越來越大。但是，不是這樣，只有在響應完成後纔會出現文件。

在服務器端，我使用response.outputstream.write方法發送塊。

如何避免在慢速連接上對較大的文件進行時間消耗？

Answer 1

我發現，只有當您發送POST請求時纔會發生這種情況。我將參數改爲URL查詢字符串的一部分，分塊下載現在可以工作。

Public Shared Function DownloadFileWithQueryString(ByVal httpPath As String, ByVal storePath As String, querystring As String) As String 
    Try 
     Dim theResponse As HttpWebResponse 
     Dim theRequest As HttpWebRequest 
     Dim fullurl As String = httpPath & "?" & querystring 
     theRequest = HttpWebRequest.Create(fullurl) 


     If My.Settings.ProxyURL <> "" Then 
      Dim prx As New WebProxy(My.Settings.ProxyURL) 
      theRequest.Proxy = prx 
     End If 




     theResponse = theRequest.GetResponse 

     Dim length As Double = theResponse.ContentLength 




     Dim writeStream As New IO.FileStream(storePath, IO.FileMode.Create) 


     Dim nRead As Integer 

     Dim readBytes(4095) As Byte 
     Dim bytesread As Integer = theResponse.GetResponseStream.Read(readBytes, 0, 4096) 



     Do Until bytesread = 0 



      'speedtimer.Start() 


      nRead += bytesread 



      writeStream.Write(readBytes, 0, bytesread) 


      bytesread = theResponse.GetResponseStream.Read(readBytes, 0, 4096) 
     Loop 

     'Close the streams 
     theResponse.GetResponseStream.Close() 
     writeStream.Close() 


     Return "OK" 
    Catch ex As Exception 
     Return ex.Message 
    End Try 
End Function