Download structure fails

[bergerkiller]

Hello all.

I am totally into structures at this point, mostly because of their simplicity in use.

I am now working on a "download structure", which allows you to download and keep track on a file.

This is the code:

  Public Structure FileDownload
        Sub New(ByVal URL As String, ByVal DestFilePath As String)
            Me.URL = URL
            Me._percent = 0
            Me.DownloadSize = Net.WebRequest.Create(Me.URL).GetResponse.ContentLength
            Me.DownloadedSize = 0
            Me.Percent = 0
            Me.DestinationFile = DestFilePath
            Me.client = New Net.WebClient
        End Sub
        Sub StartDownload()
            client.DownloadFileAsync(New Uri(Me.URL), Me.DestinationFile)
        End Sub
        Sub StopDownload(ByVal DeleteFile As Boolean)
            On Error Resume Next
            Me.client.CancelAsync()
            If DeleteFile = True And System.IO.File.Exists(Me.DestinationFile) Then
                SetAttr(Me.DestinationFile, FileAttribute.Normal)
                System.IO.File.Delete(Me.DestinationFile)
                Me.DownloadedSize = 0
            End If
            Me.Percent = 0
        End Sub
        Private _percent As Single
        Public Property Percent() As Single
            Get
                If System.IO.File.Exists(Me.DestinationFile) And Me.DownloadSize <> 0 Then
                    Me._percent = Me.DownloadedSize * 100 / Me.DownloadSize
                Else
                    Me._percent = 0
                End If
                Return Me._percent
            End Get
            Set(ByVal value As Single)
                Me._percent = value
            End Set
        End Property
        Private _DownloadedSize As Long
        Public Property DownloadedSize() As Long
            Get
                Try
                    Me._DownloadedSize = New System.IO.FileInfo(Me.DestinationFile).Length
                Catch
                    Me._DownloadedSize = 0
                End Try
                Return Me._DownloadedSize
            End Get
            Set(ByVal value As Long)
                Me._DownloadedSize = value
            End Set
        End Property
        Private client As Net.WebClient
        Public DestinationFile As String
        Public URL As String
        Public DownloadSize As Long
    End Structure

It all seems to work fine using the following thread to download a file:

d = New FileDownload("http://www.myurl.com/url/to/download.exe", My.Computer.FileSystem.SpecialDirectories.Desktop & "\download.exe")      
d.StartDownload()     
Do While d.DownloadedSize < d.DownloadSize
         ProgressbarAdapter(d.Percent, d.DownloadedSize & "/" & d.DownloadSize & " (" & d.Percent & "&#37;)")
         Threading.Thread.Sleep(200) 
Loop

Now my big problem:
The second time I download the file, the file is made but the downloaded bytes stay 0. I carefully delete the file and then start it again. Somehow it can't download the file, but no error is given. Only after a while it crashes.
If I then restart it, it just downloads the file.

Soo...what is the reason I can't download the same file to the same location twice while the program is running?

This is really a weird bug

EDIT:

It ALWAYS happens when twice downloading the same file. Changing the output file won't solve it. Really need help at this point.

[jmcilhinney]

The first thing you need to do is to get rid of that On Error Resume Next and never use it again. If you believe that an exception can reasonably be thrown in your code then use a Try...Catch block to catch that exception specifically.

Secondly, I would suggest that that type should be a class rather than a structure. Look at the .NET Framework and the types it contains and consider what's a class and what's a structure. Any type with as much functionality as yours would be a class.

Once you've made those changes, your issue will probably either go away or you'll have a better idea of exactly what the cause is.

[formlesstree4]

You can look in my signature for a Download Managing System and use it/borrow code from it.

[bergerkiller]

Yes I know of the error resume next, thats why I only use it when I have multiple commands that HAVE to be executed. If I put it all in one try block, and the first delete command fails, it doesnt continue wit hthe other stuff.

Just a way to prevent placing every command in a try block

Andd...I just found out it isn't related to my structure.
I made a download thread without my structure (using a webclient), and it fails the second time I start.

I think the webclient can only download a file once...

Any other suggestions to download files?

[formlesstree4]

Did you look in my signature?

[jmcilhinney]

On Error Resume Next simply ignores errors and continues. If you ignore an error, how do you expect to fix it? Use proper error handling and, when you catch an exception, you can diagnose the problem and fix it. While debugging at least, no error handling at all is better than On Error Resume Next.

[bergerkiller]

I fixed all problems already. It wasn't faulty error handling, I forgot to close a "getresponse" reader, causing the current stream to remain active. Trying to get the response from an active stream is impossible, causing a time-out.

This was the line causing the trouble:
Me.DownloadSize = Net.WebRequest.Create(Me.URL).GetResponse.ContentLength
The response was embedded, so it was impossible to close it. I had to give the response his own variable and close that.


I changed my structure to a class, for everyone interested, here is my (awesome) DownloadManager class for all your download needs

Public Class DownloadManager

    Sub New(ByVal URL As String, ByVal DestPath As String)
        Me.URL = URL
        Me.DestFileName = DestPath
    End Sub
    Public URL As String = ""
    Private dfln As String = ""
    Private Paused As Boolean = False
    Private Downloading As Boolean = False
    Private dledsize As Long = 0
    Private tldlsize As Long = 0
    Private dlfin As Boolean = False
    Private etime As Long
    Private ta As New Stopwatch
    Private stopdl As Boolean = False

    Public ReadOnly Property HasFinished() As Boolean
        Get
            Return dlfin
        End Get
    End Property
    Public Property DestFileName() As String
        Get
            Return dfln
        End Get
        Set(ByVal value As String)
            If Me.Downloading = False Then dfln = value
        End Set
    End Property
    Public ReadOnly Property IsDownloading() As Boolean
        Get
            Return Downloading
        End Get
    End Property
    Public ReadOnly Property IsPaused() As Boolean
        Get
            Return Paused
        End Get
    End Property
    Public ReadOnly Property DownloadedSize() As SizeMeasure
        Get
            Return New SizeMeasure(dledsize)
        End Get
    End Property
    Public ReadOnly Property TotalDownloadSize() As SizeMeasure
        Get
            If tldlsize = 0 Then
                Dim ws As Net.WebResponse = Net.WebRequest.Create(Me.URL).GetResponse
                Me.tldlsize = ws.ContentLength
                ws.Close()
            End If
            Return New SizeMeasure(tldlsize)
        End Get
    End Property
    Public ReadOnly Property Percentage() As Single
        Get
            If Me.tldlsize > 0 Then
                Dim ti As Integer = dledsize * 1000 / tldlsize
                Return ti / 10
            Else
                Return 0
            End If
        End Get
    End Property
    Public ReadOnly Property DownloadSpeed() As SpeedMeasure
        Get
            If etime <> 0 And Me.Downloading = True And Me.Paused = False Then
                Return New SpeedMeasure(dledsize * 1000 / etime)
            Else
                Return New SpeedMeasure(0)
            End If
        End Get
    End Property
    Public ReadOnly Property ElapsedTime() As TimeMeasure
        Get
            Return New TimeMeasure(etime)
        End Get
    End Property
    Public ReadOnly Property RemainingTime() As TimeMeasure
        Get
            If Me.Paused = False And Me.Downloading = True Then
                Dim remainingbytes As Long = Me.tldlsize - Me.dledsize
                Dim speed As Long = DownloadSpeed.BAS
                If speed = 0 Then speed = 1
                Return New TimeMeasure(remainingbytes * 1000 / speed)
            Else
                Return New TimeMeasure(0)
            End If
        End Get
    End Property
    Public Structure TimeMeasure
        Sub New(ByVal Msecs As Long)
            LoadTime(Msecs)
        End Sub
        Public Sub LoadTime(ByVal MiliSeconds As Long)
            If MiliSeconds < 0 Then MiliSeconds = 0
            Me.TotalMiliSeconds = MiliSeconds
            Me.Hours = Int(MiliSeconds / 3600000)
            Me.Minutes = Int(MiliSeconds / 60000) - Me.Hours * 3600
            Me.Seconds = Int(MiliSeconds / 1000) - Me.Minutes * 60 - Me.Hours * 3600
            Dim hstr As String = Me.Hours
            Dim mstr As String = Me.Minutes
            Dim sstr As String = Me.Seconds
            If hstr.Length = 1 Then hstr = "0" & hstr
            If mstr.Length = 1 Then mstr = "0" & mstr
            If sstr.Length = 1 Then sstr = "0" & sstr
            Me.TimeStringHMS = hstr & ":" & mstr & ":" & sstr
            If Me.Hours > 0 Then
                Me.TimeStringS = Int(MiliSeconds / 360000) & " hours"
            ElseIf Me.Minutes > 0 Then
                Me.TimeStringS = Int(MiliSeconds / 60000) & " minutes"
            Else
                Me.TimeStringS = Int(MiliSeconds / 1000) & " seconds"
            End If
        End Sub
        Public TimeStringHMS As String
        Public TimeStringS As String
        Public TotalMiliSeconds As Long
        Public Seconds As Long
        Public Minutes As Long
        Public Hours As Long
    End Structure
    Public Structure SpeedMeasure
        Sub New(ByVal BAS As Long)
            LoadSpeed(BAS)
        End Sub
        Public Sub LoadSpeed(ByVal BAS As Long)
            Me.BAS = BAS
            Me.KBAS = BAS / 1000
            Me.MBAS = BAS / 1000000
            If BAS > 1000000 Then
                Me.SpeedString = Me.MBAS & " MB/s"
            ElseIf BAS > 1000 Then
                Me.SpeedString = Me.KBAS & " KB/s"
            Else
                Me.SpeedString = Me.BAS & " B/s"
            End If
        End Sub
        Public SpeedString As String
        Public BAS As Long
        Public KBAS As Long
        Public MBAS As Long
    End Structure
    Public Structure SizeMeasure
        Sub New(ByVal Bytes As Long)
            LoadSize(Bytes)
        End Sub
        Public Sub LoadSize(ByVal Bytes As Long)
            Me.Bytes = Bytes
            Me.KBytes = Bytes / 1000
            Me.MBytes = Bytes / 1000000
            Me.GBytes = Bytes / 1000000000
            If Bytes > 1000000000 Then
                SizeString = Me.GBytes & " GB"
            ElseIf Bytes > 1000000 Then
                SizeString = Me.MBytes & " MB"
            ElseIf Bytes > 1000 Then
                SizeString = Me.KBytes & " KB"
            Else
                SizeString = Me.Bytes & " bytes"
            End If
        End Sub
        Public SizeString As String
        Public Bytes As Long
        Public KBytes As Long
        Public MBytes As Long
        Public GBytes As Long
    End Structure

    Private t As Threading.Thread
    Public Sub StartDownload()
        If Me.Downloading = False Then Me.Paused = False
        If Me.Paused = False And Me.Downloading = False Then
            Try
                t = New Threading.Thread(AddressOf DownLoadProcess)
                t.IsBackground = True
                t.Start()
            Catch ex As Exception
                MsgBox(ex.Message & vbCrLf & vbCrLf & "Failed to start your download.", MsgBoxStyle.Critical)
            End Try
        Else
            Me.Paused = False
        End If
    End Sub
    Public Sub PauseDownload()
        Me.Paused = True
    End Sub
    Public Sub StopDownload()
        Me.stopdl = True
    End Sub

    Private Sub DownLoadProcess()
        Try
            Me.Downloading = True
            Me.dlfin = False
            Me.dledsize = 0
            If System.IO.File.Exists(Me.DestFileName) Then
                SetAttr(Me.DestFileName, FileAttribute.Normal)
                System.IO.File.Delete(Me.DestFileName)
            End If
            Dim ws As Net.WebResponse = Net.WebRequest.Create(Me.URL).GetResponse
            Me.tldlsize = ws.ContentLength
            If Me.tldlsize > 0 Then
                Dim str As IO.Stream = ws.GetResponseStream()
                Dim inBuf(10000000) As Byte
                Dim bytesToRead As Integer = Me.tldlsize
                Dim fstr As New IO.FileStream(Me.DestFileName, IO.FileMode.OpenOrCreate, IO.FileAccess.Write)
                'Dim lastw As Long = 0
                Dim t As New Stopwatch
                Dim oldet As Long = 0
                While bytesToRead > 0
                    If Me.stopdl = True Then Exit While
                    If Me.Paused = False Then
                        t.Start()
                        oldet = etime
                        Dim count As Long = 10000000
                        If bytesToRead < 10000000 Then count = bytesToRead
                        Dim n As Integer = str.Read(inBuf, 0, count)
                        If n = 0 Then Exit While
                        Me.dledsize += n
                        bytesToRead -= n
                        fstr.Write(inBuf, 0, n)
                        etime = t.ElapsedMilliseconds
                    Else
                        t.Stop()
                    End If
                End While
                t.Stop()
                etime = t.ElapsedMilliseconds
                fstr.Close()
                ws.Close()
                str.Close()
            Else
                MsgBox("Failed to start your download because the link is invalid.", MsgBoxStyle.Critical)
            End If
        Catch ex As Exception
            MsgBox("Failed to start your download. " & vbCrLf & vbCrLf & ex.Message, MsgBoxStyle.Critical)
        End Try
        If Me.stopdl = True Then
            Try
                System.IO.File.Delete(Me.DestFileName)
            Catch
            End Try
        End If
        Me.stopdl = False
        Me.Downloading = False
        Me.dlfin = True
    End Sub
End Class

It has all features you would possibly need: download speed, size and downloaded size, percentage, remaining and elapsed download time, pause download feature, and all with special enhancements for displaying speed, time and size.