VB.NET FTP下载文件损坏

Question

我想下载FTP站点上的所有文件。我闯入2个操作。首先是获取目录中所有文件的列表。然后我继续下载每个文件。但不幸的是，下载的文件已损坏。最糟糕的是，它会影响FTP文件夹上的文件。两个文件夹都包含损坏的文件。从查看缩略图图像到默认图像缩略图。这是怎么发生的并克服这个问题？以下是我的代码;完整的代码类。我作为提供参考和指导做了正确的方式:)

Private strTargetPath As String 
Private strDestPath As String 

Private Sub frmLoader_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load 
    Try 
     objSQL = New clsSQL 
     If objSQL.SQLGetAllData Then 'Get data from SQL and insert into an arraylist 
      strTargetPath = "ftp://192.168.1.120/image/" 
      strDestPath = "D:\Application\FTPImg\" 
      ListFileFromFTP() 
     End If 
    Catch ex As Exception 
     strErrMsg = "Oops! Something is wrong with loading login form." 
     MessageBox.Show(strErrMsg & vbCrLf & "ExMsg: " & ex.Message, "Error message!", MessageBoxButtons.OK, MessageBoxIcon.Error) 
    End Try 
End Sub 
Private Sub ListFileFromFTP() 
    Dim arrFile As ArrayList 
    Dim strPath As String 
    Try 
     Dim reqFTP As FtpWebRequest 
     reqFTP = FtpWebRequest.Create(New Uri(strTargetPath)) 
     reqFTP.UseBinary = True 
     reqFTP.Credentials = New NetworkCredential("user", "user123") 
     reqFTP.Method = WebRequestMethods.Ftp.ListDirectory 
     reqFTP.Proxy = Nothing 
     reqFTP.KeepAlive = False 
     reqFTP.UsePassive = False 
     Dim response As FtpWebResponse = DirectCast(reqFTP.GetResponse(), FtpWebResponse) 
     Dim sr As StreamReader 
     sr = New StreamReader(reqFTP.GetResponse().GetResponseStream()) 
     Dim FileListing As String = sr.ReadLine 
     arrFile = New ArrayList 
     While FileListing <> Nothing 
      strPath = strTargetPath & FileListing 
      arrFile.Add(strPath) 
      FileListing = sr.ReadLine 
     End While 
     sr.Close() 
     sr = Nothing 
     reqFTP = Nothing 
     response.Close() 
     For i = 0 To (arrFile.Count - 1) 
      DownloadImage(arrFile.Item(i)) 
     Next 
    Catch ex As Exception 
     strErrMsg = "Oops! Something is wrong with ListFileFromFTP." 
     MessageBox.Show(strErrMsg & vbCrLf & "ExMsg: " & ex.Message, "Error message!", MessageBoxButtons.OK, MessageBoxIcon.Error) 
    End Try 
End Sub 
Public Function DownloadImage(ByVal strName As String) As String 
    Dim ftp_request As FtpWebRequest = Nothing 
    Dim ftpStream As Stream = Nothing 

    Dim strOldName As String 
    Dim strNewName As String 
    Dim withoutextension As String 
    Dim extension As String 
    Try 
     strOldName = strTargetPath & strName 
     withoutextension = Path.GetFileNameWithoutExtension(strOldName) 
     extension = Path.GetExtension(strOldName) 
     strNewName = strDestPath & withoutextension & extension 

     ftp_request = CType(System.Net.FtpWebRequest.Create(strName), System.Net.FtpWebRequest) 
     ftp_request.Method = System.Net.WebRequestMethods.Ftp.UploadFile 
     ftp_request.Credentials = New System.Net.NetworkCredential("user", "user123") 
     ftp_request.UseBinary = True 
     ftp_request.KeepAlive = False 
     ftp_request.Proxy = Nothing 
     Dim response As FtpWebResponse = DirectCast(ftp_request.GetResponse(), FtpWebResponse) 
     Dim responseStream As IO.Stream = response.GetResponseStream 

     Dim fs As New IO.FileStream(strNewName, IO.FileMode.Create) 
     Dim buffer(2047) As Byte 
     Dim read As Integer = 0 
     Do 
      read = responseStream.Read(buffer, 0, buffer.Length) 
      fs.Write(buffer, 0, read) 
     Loop Until read = 0 
     responseStream.Close() 
     fs.Flush() 
     fs.Close() 
     responseStream.Close() 
     response.Close() 
    Catch ex As WebException 
     Dim response As FtpWebResponse = ex.Response 
     If response.StatusCode = FtpStatusCode.ActionNotTakenFileUnavailable Then 
      MsgBox(response.StatusDescription) 
      Return String.Empty 
     Else 
      MsgBox(response.StatusDescription) 
     End If 
    End Try 
End Function 

对于下载文件，这是取得成功的正确代码：

Private Sub Download(ByVal strFTPPath As String) 
     Dim reqFTP As FtpWebRequest = Nothing 
     Dim ftpStream As Stream = Nothing 
     Try 
      Dim outputStream As New FileStream(strDestPath & strImgName, FileMode.Create) 
      reqFTP = DirectCast(FtpWebRequest.Create(New Uri(strFTPPath)), FtpWebRequest) 
      reqFTP.Method = WebRequestMethods.Ftp.DownloadFile 
      reqFTP.UseBinary = True 
      reqFTP.Credentials = New NetworkCredential("user", "user123") 
      Dim response As FtpWebResponse = DirectCast(reqFTP.GetResponse(), FtpWebResponse) 
      ftpStream = response.GetResponseStream() 
      Dim cl As Long = response.ContentLength 
      Dim bufferSize As Integer = 2048 
      Dim readCount As Integer 
      Dim buffer As Byte() = New Byte(bufferSize - 1) {} 

      readCount = ftpStream.Read(buffer, 0, bufferSize) 
      While readCount > 0 
       outputStream.Write(buffer, 0, readCount) 
       readCount = ftpStream.Read(buffer, 0, bufferSize) 
      End While 
      ftpStream.Close() 
      outputStream.Close() 
      response.Close() 
     Catch ex As Exception 
      If ftpStream IsNot Nothing Then 
       ftpStream.Close() 
       ftpStream.Dispose() 
      End If 
      Throw New Exception(ex.Message.ToString()) 
     End Try 
    End Sub 

Answer 1

有一些奇怪的事情在你的代码。您正在关闭responseStream两次。

而你正在使用ftp请求方法uploadFile。但随后下载它。

而不是使用ftp的东西使用这个来代替。它更简单，你将缓冲区和数据流外包给微软，这应该比我们少一些。

Dim webClient = new WebClient() 
webClient.Credentials = new NetworkCredential("user", "user123") 
dim response = webClient.UploadFile("ftp://MyFtpAddress","c:\myfile.jpg") 
dim sResponse = System.Text.Encoding.Default.GetString(response)