如果文件不存在于给定的本地文件列表中，则从 FTP 下载文件

我有一个 FTP 服务器，我想从中下载本地目录中不存在的所有文件。

我尝试做一个For Next但我就是无法理解它。我尝试枚举这些文件，但由于对两个列表都执行了该操作，所以出现错误。我认为该错误可能是由于交叉检查在线文件与本地列表中的单个枚举文件引起的。我该如何消除这个问题？

FTPClient 类代码链接：

https://docs.google.com/file/d/0BxFwEuHe1g77TEw2ckZxVUlQdGM/edit?usp=sharing https://docs.google.com/file/d/0BxFwEuHe1g77TEw2ckZxVUlQdGM/edit?usp=sharing

所有代码：

          Dim ftp As New FTPclient("ftp://www.ahpg.zxq.net", "eg", "eg")

    Dim dirList As FTPdirectory = ftp.ListDirectoryDetail("/")
    Dim result As List(Of String) = ftp.ListDirectory("/")
    For Each line As String In result
        FTPLBX.Items.Add(line)
    Next
    Dim str As String
    Dim locstr As String
    Dim res_numer As IEnumerator
    res_numer = result.GetEnumerator()
    Dim loclist As List(Of String) = New List(Of String) _
                                     (System.IO.Directory.EnumerateFiles("C:/Program Files/Business Elements/Recent Files"))
    Dim LOC_Enum As IEnumerator
    LOC_Enum = loclist.GetEnumerator
    Do While LOC_Enum.MoveNext
        locstr = (LOC_Enum.Current)
    Loop
    Do While (res_numer.MoveNext)
        str = (res_numer.Current)
    Loop

    For Each str In loclist
        If Not loclist.Contains(str) = True Then
            My.Computer.Network.DownloadFile("ftp://www.ahpg.zxq.net/ftpfiles/" & str.ToString, _
                                             "C:/Program Files/Business Elements/Recent Files/" & str.ToString, "eg", "eg")
            MessageBox.Show("Done ")
        End If
    Next

End Sub

如果它对你有用的话，我让它变得更容易一些。干得好：

    ' Your instance of FTPClient
    Dim ftp As New FTPclient("ftp://www.ahpg.zxq.net", "eg", "eg")

    ' The path to destination folder (Local directory)
    Dim localDir As String = "C:/Program Files/Business Elements/Recent Files/"

    ' Lists all the file in the given directory of FTP server
    For Each file As FTPfileInfo In ftp.ListDirectoryDetail("/").GetFiles

        Try
            ftp.Download(file, localDir & file.Filename)

            ' The FTPClient class throws exception if the 
            ' file already exists in destination directory
        Catch e As ApplicationException
            Console.WriteLine(e.Message)
        End Try
    Next file

Note 1: 我下载了FTPClient http://www.codeproject.com/Articles/11991/An-FTP-client-library-for-NET-2-0班级来自CodeProject http://www.codeproject.com/但它与您在问题中提供的几乎相同。

Note 2: The FTPClient http://www.codeproject.com/Articles/11991/An-FTP-client-library-for-NET-2-0如果目标文件夹中存在该文件，它本身会引发异常。因此您无需费心比较文件。

Note 3: 注意后面的slash在......的最后locadDir细绳。如果没有，该文件将被下载到商业元素 folder.