将C＃转换为VB.Net，未在下载的文件中添加字节

Question

I've converted a code from C# to vb.net, however the converted code doesn't update the file (eg: add bytes to the saved file) while the original C# code works. I am not knowledgeable in C# so I used an online converter to convert the code, tried fixing unconverted codes but to no avail.

[original c# code]

  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();
                    }
                }

[converted c# to vb.net code]

  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()

My issue is that, this code, writes the file from "sUrlToReadFileFrom" properly to "sFilePathToWriteFileTo" but the zip file is always 0 bytes and the Background worker loops without adding any byte to the file.

Answer 1

You can't assign within an expression in VB. That is, you have to extract out the folowing assignment before the loop and within the loop at the end of the loop:

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

The equivalent VB code is:

    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

The problem is this line:

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

It performs what's called inline assignment , which means that it assigns the result of streamRemote.Read() to iByteSize in the middle of a statement and then returns the result of that.

VB.NET doesn't support this, which probably is why the converter you have used removed it. Thus iByteSize will always be 0, and no bytes are written to the file.

The fix is to set the iByteSize variable separately before you enter the loop, and at the last line of the loop:

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

Also, the request and response variables doesn't appear to be used anywhere. If this is the case you should remove them.

Answer 3

Try this:

   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

The InlineAssignHelper :

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