Question

我想通过附加文件恢复下载，问题是它使文件变大，例如文件A大小为98000kb，当程序下载文件A时，互联网问题或用户中止下载和下载停在2000kb。然后用户继续进行恢复下载，恢复下载，但文件A大小已变为100000 kb。有没有办法解决这个问题？这是我的代码：

    Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork        
    Dim url As String = e.Argument
    'Creating the request and getting the response
    Dim strFileName
    Dim a As String
    Dim b() As String
    files = url.Split(CChar(","))
    For Each a In files
        b = a.Split("/")
        strFileName = b(b.Length - 1)
        Me.whereToSave = "C:\Temp\" & strFileName
    Next

    Dim sDestinationPath As String = me.whereToSave 'file destination

    Dim iFileSize As Long = 0
    Dim iBufferSize As Integer = 1024
    iBufferSize *= 1000
    Dim iExistLen As Long = 0
    Dim saveFileStream As System.IO.FileStream = Nothing

    Dim hwRq As System.Net.HttpWebRequest
    Dim hwRes As System.Net.HttpWebResponse
    hwRq = DirectCast(System.Net.HttpWebRequest.Create(url), System.Net.HttpWebRequest)
    hwRq.AddRange(CInt(iExistLen))
    Dim smRespStream As System.IO.Stream
    hwRes = DirectCast(hwRq.GetResponse(), System.Net.HttpWebResponse)
    smRespStream = hwRes.GetResponseStream()

    iFileSize = hwRes.ContentLength
    If System.IO.File.Exists(sDestinationPath) Then
        Dim fINfo As New System.IO.FileInfo(sDestinationPath)
        iExistLen = fINfo.Length
    End If

    If iExistLen = iFileSize Then
        MsgBox("exists")
        saveFileStream = New System.IO.FileStream(sDestinationPath, System.IO.FileMode.Open, IO.FileAccess.Write, System.IO.FileShare.Read)
    ElseIf iExistLen > 0 And iExistLen <= iFileSize Then
        MsgBox("Append")
        saveFileStream = New System.IO.FileStream(sDestinationPath, System.IO.FileMode.Append, System.IO.FileAccess.Write, System.IO.FileShare.ReadWrite)
    Else
        MsgBox("Create")
        saveFileStream = New System.IO.FileStream(sDestinationPath, System.IO.FileMode.Create, System.IO.FileAccess.Write, System.IO.FileShare.ReadWrite)
    End If
    Dim iByteSize As Integer
    Dim downBuffer As Byte() = New Byte(iBufferSize - 1) {}
    Dim safedelegate As New ChangeTextsSafe(AddressOf ChangeTexts)
    iByteSize = (smRespStream.Read(downBuffer, 0, downBuffer.Length))
    While (iByteSize > 0)
        saveFileStream.Write(downBuffer, 0, iByteSize)
        iByteSize = (smRespStream.Read(downBuffer, 0, downBuffer.Length))
    End While

Answer 1

在检查文件是否已存在并设置其长度之前，您正在设置hwRq.AddRange(CInt(iExistLen))。

移动此

If System.IO.File.Exists(sDestinationPath) Then
        Dim fINfo As New System.IO.FileInfo(sDestinationPath)
        iExistLen = fINfo.Length
    End If

高于hwRq.AddRange(CInt(iExistLen))

的定义

使用stream.addrange继续下载

1 个答案: