将C＃转换为VB.Net，未在下载的文件中添加字节

Question

我已经将代码从C＃转换为vb.net，但是在原始C＃代码有效的情况下，转换后的代码不会更新文件（例如：将字节添加到保存的文件中）。 我不懂C＃，所以我使用了在线转换器来转换代码，尝试修复未转换的代码，但无济于事。

[原始的C＃代码]

  if (serverVersion > localVersion)
            {
                Uri url = new Uri(sUrlToReadFileFrom);
                System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(url);
                System.Net.HttpWebResponse response = (System.Net.HttpWebResponse)request.GetResponse();
                response.Close();

                Int64 iSize = response.ContentLength;

                Int64 iRunningByteTotal = 0;

                using (System.Net.WebClient client = new System.Net.WebClient())
                {
                    using (System.IO.Stream streamRemote = client.OpenRead(new Uri(sUrlToReadFileFrom)))
                    {
                        using (Stream streamLocal = new FileStream(sFilePathToWriteFileTo, FileMode.Create, FileAccess.Write, FileShare.None))
                        {
                            int iByteSize = 0;
                            byte[] byteBuffer = new byte[iSize];
                            while ((iByteSize = streamRemote.Read(byteBuffer, 0, byteBuffer.Length)) > 0)
                            {
                                streamLocal.Write(byteBuffer, 0, iByteSize);
                                iRunningByteTotal += iByteSize;

                                double dIndex = (double)(iRunningByteTotal);
                                double dTotal = (double)byteBuffer.Length;
                                double dProgressPercentage = (dIndex / dTotal);
                                int iProgressPercentage = (int)(dProgressPercentage * 100);

                                backgroundWorker1.ReportProgress(iProgressPercentage);
                            }

                            streamLocal.Close();
                        }

                        streamRemote.Close();
                    }
                }

[将C＃转换为vb.net代码]

  If (serverVersion > localVersion) Then
                Dim url As Uri = New Uri(sUrlToReadFileFrom)
                Dim request As HttpWebRequest = CType(WebRequest.Create(url), HttpWebRequest)
                Dim response As HttpWebResponse = CType(request.GetResponse, HttpWebResponse)
                response.Close()

                Dim iSize As Int64 = response.ContentLength
                Dim iRunningByteTotal As Int64 = 0

                Dim client As System.Net.WebClient = New System.Net.WebClient
                Dim streamRemote As System.IO.Stream = client.OpenRead(New Uri(sUrlToReadFileFrom))
                Dim streamLocal As Stream = New FileStream(sFilePathToWriteFileTo, FileMode.CreateNew, FileAccess.ReadWrite, FileShare.None)

                Dim iByteSize As Integer = 0
                Dim byteBuffer() As Byte = New Byte((iSize) - 1) {}

                While (streamRemote.Read(byteBuffer, 0, byteBuffer.Length) > 0)
                    streamLocal.Write(byteBuffer, 0, iByteSize)
                    iRunningByteTotal = iRunningByteTotal + iByteSize

                    Dim dIndex = CType((iRunningByteTotal), Double)
                    Dim dTotal = CType(byteBuffer.Length, Double)
                    Dim dProgressPercentage As Double = (dIndex / dTotal)
                    Dim iProgressPercentage As Integer = CType((dProgressPercentage * 100), Integer)


                    bgMain.ReportProgress(iProgressPercentage)

                    'status.Text = "Downloading updatess " & dIndex & " of " & dTotal

                End While

                streamLocal.Close()
                streamRemote.Close()

我的问题是，此代码将文件从“ sUrlToReadFileFrom”正确写入“ sFilePathToWriteFileTo”，但zip文件始终为0字节，并且后​​台工作程序循环而未在文件中添加任何字节。

Answer 1

您不能在VB中的表达式内赋值。 也就是说，您必须在循环之前和循环结束时在循环内提​​取以下分配：

iByteSize = streamRemote.Read(byteBuffer, 0, byteBuffer.Length)

等效的VB代码为：

    If serverVersion > localVersion Then
        Dim url As New Uri(sUrlToReadFileFrom)
        Dim request As System.Net.HttpWebRequest = CType(System.Net.WebRequest.Create(url), System.Net.HttpWebRequest)
        Dim response As System.Net.HttpWebResponse = CType(request.GetResponse(), System.Net.HttpWebResponse)
        response.Close()

        Dim iSize As Int64 = response.ContentLength

        Dim iRunningByteTotal As Int64 = 0

        Using client As New System.Net.WebClient()
            Using streamRemote As System.IO.Stream = client.OpenRead(New Uri(sUrlToReadFileFrom))
                Using streamLocal As Stream = New FileStream(sFilePathToWriteFileTo, FileMode.Create, FileAccess.Write, FileShare.None)
                    Dim iByteSize As Integer = 0
                    Dim byteBuffer(iSize - 1) As Byte
                    iByteSize = streamRemote.Read(byteBuffer, 0, byteBuffer.Length)
                    Do While iByteSize > 0
                        streamLocal.Write(byteBuffer, 0, iByteSize)
                        iRunningByteTotal += iByteSize

                        Dim dIndex As Double = CDbl(iRunningByteTotal)
                        Dim dTotal As Double = CDbl(byteBuffer.Length)
                        Dim dProgressPercentage As Double = (dIndex / dTotal)
                        Dim iProgressPercentage As Integer = CInt(Math.Truncate(dProgressPercentage * 100))

                        backgroundWorker1.ReportProgress(iProgressPercentage)
                        iByteSize = streamRemote.Read(byteBuffer, 0, byteBuffer.Length)
                    Loop

                    streamLocal.Close()
                End Using

                streamRemote.Close()
            End Using
        End Using

Answer 2

问题是这一行：

while ((iByteSize = streamRemote.Read(byteBuffer, 0, byteBuffer.Length)) > 0)

它执行所谓的内联分配 ，这意味着它在语句的中间将streamRemote.Read()的结果分配给iByteSize ，然后返回该结果。

VB.NET不支持此功能，这可能就是您使用的转换器删除了它的原因。 因此， iByteSize将始终为0，并且没有字节写入文件。

解决方法是在进入循环之前和循环的最后一行分别设置iByteSize变量：

iByteSize = streamRemote.Read(byteBuffer, 0, byteBuffer.Length)

While iByteSize > 0
    ...the rest of your code...

    'Put this last:
    iByteSize = streamRemote.Read(byteBuffer, 0, byteBuffer.Length)
End While

同样， request和response变量似乎没有在任何地方使用。 如果是这种情况，则应将其删除。

Answer 3

尝试这个：

   If serverVersion > localVersion Then
        Dim url As New Uri(sUrlToReadFileFrom)
        Dim request As System.Net.HttpWebRequest = DirectCast(System.Net.WebRequest.Create(url), System.Net.HttpWebRequest)
        Dim response As System.Net.HttpWebResponse = DirectCast(request.GetResponse(), System.Net.HttpWebResponse)
        response.Close()

        Dim iSize As Int64 = response.ContentLength

        Dim iRunningByteTotal As Int64 = 0

        Using client As New System.Net.WebClient()
            Using streamRemote As System.IO.Stream = client.OpenRead(New Uri(sUrlToReadFileFrom))
                Using streamLocal As Stream = New FileStream(sFilePathToWriteFileTo, FileMode.Create, FileAccess.Write, FileShare.None)
                    Dim iByteSize As Integer = 0
                    Dim byteBuffer As Byte() = New Byte(iSize - 1) {}
                    While (InlineAssignHelper(iByteSize, streamRemote.Read(byteBuffer, 0, byteBuffer.Length))) > 0
                        streamLocal.Write(byteBuffer, 0, iByteSize)
                        iRunningByteTotal += iByteSize

                        Dim dIndex As Double = CDbl(iRunningByteTotal)
                        Dim dTotal As Double = CDbl(byteBuffer.Length)
                        Dim dProgressPercentage As Double = (dIndex / dTotal)
                        Dim iProgressPercentage As Integer = CInt(dProgressPercentage * 100)

                        backgroundWorker1.ReportProgress(iProgressPercentage)
                    End While

                    streamLocal.Close()
                End Using

                streamRemote.Close()
            End Using
        End Using
    End If

InlineAssignHelper ：

Private Shared Function InlineAssignHelper(Of T)(ByRef target As T, ByVal value As T) As T
  target = value
  Return value
End Function