Downloading multiple files

[Marivic]

Hi Experts,

I was asked to develop a simple file downloading utility from the server to the client's side. But all that I had came up is downloading of file one by one.

This is the scenario:

I had listed the files to be downloaded in a listbox and the user will select files to download. However, the user must have a choice to download all files or selecting mutiple files. It's too tiresome for the user to download one by one file that he needed. My application displays a dialog box for the user to save the file.

Below is how I call the function to download multiple selected files.

Dim item As ListItem
 
        For Each item In ListBox1.Items
 
            If item.Selected Then
 
                DownloadFile(Session("userdir") & item.Text, False)
 
            End If
 
        Next

But after downloading the first file, it's not asking for the next selected file.

I didn't want to download files at the same time. What I wanted is to download file right after the other.

Any help will be greatly appreciated.

Thanks in advance.

[hellswraith]

Ok, I know your using VB.Net, but if you would like, I have a download class I built in C#. All you do is pass in an string array of links to download and the path to save them to, then call the startdownload method.

Each time a download completes, an event is raised telling you which one was just downloaded, the total amount it is downloading, and how many have been downloaded so far.

It works well for me.

Here is the dll. Just add a reference to it in your project, and you can create an instance of it.

I also suggest that you call the StartDownload method in its own thread that way your app won't lock up. You will know when it is done downloading by the event it fires. If the amount downloaded is the same as the total to download, then that was the last download that just happened. Also, check the success value of the event arguments. It will tell you if there was a problem downloading the link or not.


Tell me what you think.

[Marivic]

Hello Hellwraith,

I really appreciate your help. But I still consider myself a newbie in VB.Net. I'm not asking you to do my assignment for me but I'm asking you to please help me in every step of the way.

This is my first attempt on threading and I must admit that it's not that clear to me.

Kindly take a look on my code.

Imports System.IO
Imports System.IO.Directory
Imports System.Data.SqlClient
Imports System.Object
Imports System.Threading
Imports FileDownloader
 
Public Class downfile
    Inherits System.Web.UI.Page
    Protected WithEvents Button1 As System.Web.UI.WebControls.Button
    Protected WithEvents Label1 As System.Web.UI.WebControls.Label
    Protected WithEvents Button2 As System.Web.UI.WebControls.Button
    Protected WithEvents Button3 As System.Web.UI.WebControls.Button
    Protected WithEvents Label2 As System.Web.UI.WebControls.Label
    Protected WithEvents ListBox1 As System.Web.UI.WebControls.ListBox
 
    Private fdObject As New FileDownload()
    Private theDownloadThread As Thread
 
#Region " Web Form Designer Generated Code "
 
    'This call is required by the Web Form Designer.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
 
    End Sub
 
    Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init
        'CODEGEN: This method call is required by the Web Form Designer
        'Do not modify it using the code editor.
        InitializeComponent()
    End Sub
 
#End Region
 
    Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        If Not Page.IsPostBack Then
            BindData()
        End If
    End Sub
 
    Sub BindData()
        Dim path As Path
        Dim filepath As String = Session("userdir")
        ListBox1.BorderStyle = BorderStyle.Solid
        ListBox1.BorderColor = Color.Chocolate
        Dim fileEntries As String() = Directory.GetFiles(filepath)
        Dim fileName As String = path.GetFileName(filepath)
        For Each fileName In fileEntries
            ListBox1.Items.Add(path.GetFileName(fileName))
        Next fileName
    End Sub
 
' this is my original download function
    Private Sub DownloadFile(ByVal fname As String, ByVal forceDownload As Boolean)
 
        Dim path As Path
 
        Dim fullpath = path.GetFullPath(fname)
        Dim name = path.GetFileName(fullpath)
        Dim ext = path.GetExtension(fullpath)
        Dim type As String = ""
 
        If Not IsDBNull(ext) Then
            ext = LCase(ext)
        End If
 
        Select Case ext
            Case ".htm", ".html"
                type = "text/HTML"
            Case ".txt"
                type = "text/plain"
            Case ".doc", ".rtf"
                type = "Application/msword"
            Case ".csv", ".xls"
                type = "Application/x-msexcel"
            Case Else
                type = "text/plain"
        End Select
 
        If (forceDownload) Then
            Response.AppendHeader("content-disposition", _
             "attachment; filename=" + name)
        End If
        If type <> "" Then
            Response.ContentType = type
        End If
 
        Response.WriteFile(fullpath)
        Response.End()
 
    End Sub
 
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim FilesToDownload(20) As String
        Dim ictr As Integer = 0
        Dim DownLoadItem As ListItem
       
        For Each DownLoadItem In ListBox1.Items
            If DownLoadItem.Selected Then
                FilesToDownload(ictr) = DownLoadItem.Text
                ' Response.Write(FilesToDownload(ictr))
            End If
            ictr = ictr + 1
        Next
 
        'Pass in the array to the FileDownload object.
        fdObject = New FileDownload(FilesToDownload(ictr))
 
' I dont know what's next; how to call the startdownload

Thank you for any help.

[Marivic]

Hi Hellswraith,

Pls disregard my previous post:

This is my modified function:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        ' Dim FilesToDownload() As String
        Dim FilesToDownload As New ArrayList()
        Dim DownLoadItem As ListItem
        Dim i As Integer
        For i = 0 To ListBox1.Items.Count - 1
            If ListBox1.Items(i).Selected Then
                'FilesToDownload(i) = ListBox1.Items(i).Text
                FilesToDownload.Add(ListBox1.Items(i).Text)
            End If
        Next
 
        'check items of array if correct
        Dim j As Integer
        For j = 0 To FilesToDownload.Count - 1
            Response.Write(CStr(FilesToDownload.Item(j)))
        Next
 
        'Pass in the array to the FileDownload object.
        fdObject = New FileDownload(FilesToDownload(FilesToDownload.Count - 1))
 
' how to pass array and path?? is this correct?

I've used arraylist because the exact array size cannot be determine. It's based on the user selection.

Many thanks.

[Marivic]

Hi Hellswraith,

Pls disregard my previous post:

This is my modified function:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        ' Dim FilesToDownload() As String
        Dim FilesToDownload As New ArrayList()
        Dim DownLoadItem As ListItem
        Dim i As Integer
        For i = 0 To ListBox1.Items.Count - 1
            If ListBox1.Items(i).Selected Then
                'FilesToDownload(i) = ListBox1.Items(i).Text
                FilesToDownload.Add(ListBox1.Items(i).Text)
            End If
        Next
 
        'check items of array if correct
        Dim j As Integer
        For j = 0 To FilesToDownload.Count - 1
            Response.Write(CStr(FilesToDownload.Item(j)))
        Next
 
        'Pass in the array to the FileDownload object.
        fdObject = New FileDownload(FilesToDownload(FilesToDownload.Count - 1))
 
' how to pass array and path?? is this correct?

I've used arraylist because the exact array size cannot be determine. It's based on the user selection.

Many thanks.

[hellswraith]

Well, I built this project for you in VB that shows you how to use my download class....but then I realized that you are trying to do this from the server end, is that true? If so, I have no idea how to do what you are asking.

Here is the project I built for you anyway.

[Marivic]

Hi,

Yup, the files are coming from the server. I was about to give up and conclude that downloading multiple files is not possible based on my research. But you had me on the idea of threading so I hang on a little bit.

Well, now coming from an expert, I'm now confident to tell my boss that it's really not possible.

Thank you very much for your help and effort.

I really appreciate them.