Allow download of filenames with &'s in them

[szlamany]

I want to allow users to download files that have names containing & characters.

We've escaped our way through the problem but cannot seem to get around one last obstacle.

Here in Download.asp.vb we have

Imports System.IO

Partial Class Clients_Download
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim ctx As HttpContext = HttpContext.Current
        Dim response As HttpResponse = ctx.Response
        Dim sFile As String = Request.QueryString("filename".ToString)

        ' Buffer to read 10K bytes in chunk:
        Dim buffer(10000) As Byte
        ' Length of the file:
        Dim length As Integer
        ' Total bytes to read:
        Dim dataToRead As Long
        ' Identify the file to download including its path.
        Dim filepath As String = sFile
        ' Identify the file name.
        Dim filename As String = System.IO.Path.GetFileName(filepath)

        Using iStream As New FileStream(filepath, System.IO.FileMode.Open, IO.FileAccess.Read, IO.FileShare.Read)
            ' Total bytes to read:
            dataToRead = iStream.Length

            response.ContentType = "application/octet-stream"
            response.AddHeader("Content-Disposition", "attachment; filename=" & filename)

And here is where it fails - the attachment; filename= line.

The filename vbl has the & character within it.

The pop-up that appears in the browser window asking for where to save the file shows a filename WITHOUT the &'s.

Here is the continuation of the code

            ' Read the bytes.
            While dataToRead > 0
                ' Verify that the client is connected.
                If response.IsClientConnected Then
                    ' Read the data in buffer
                    length = iStream.Read(buffer, 0, 10000)

                    ' Write the data to the current output stream.
                    response.OutputStream.Write(buffer, 0, length)

                    ' Flush the data to the HTML output.
                    response.Flush()

                    ReDim buffer(10000) ' Clear the buffer
                    dataToRead = dataToRead - length
                Else
                    'prevent infinite loop if user disconnects
                    dataToRead = -1
                End If
            End While

            iStream.Close()

            'delete the file after downloading it
            If Request.QueryString("delfile") = "true" Then
                'make sure it contains \temp\ dir
                If sFile.Contains("\temp\") Then
                    File.Delete(sFile)
                End If
            End If
            response.End()
        End Using
    End Sub

[Pradeep1210]

It works ok for me.

I assume this is a typo,
Dim sFile As String = Request.QueryString("filename".ToString)
and should be changed to:
Dim sFile As String = Request.QueryString("filename").ToString


This is what I get, running your code as it is.

In the first box, filename is in a label, so it assumes & as shortcut and shows as underscore. But in the actual box where I specify filename to save, I can see the "&" in filename.

[Harsh Gupta]

Hey,

You can try your luck with HttpServerUtility.HtmlEncode Method. This will convert characters to their respective HTML Hex format.

[Pradeep1210]

BTW how big are your files? Why do you need to read/write in chunks?

This code is a simple one-liner and has always worked for me:

Sub TransmitFile(ByVal fileName As String)
    Response.ContentType = "application/octet-stream"
    Response.AddHeader("Content-Disposition", "attachment; filename=""" & System.IO.Path.GetFileName(fileName) & """")
    Try
        Response.TransmitFile(fileName)
    Catch ex As Exception
        Response.Write(ex.ToString)
    End Try
End Sub
 
Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim fileName As String = "C:\Temp\abc&d.txt"
    TransmitFile(fileName)
End Sub

[techgnome]

I'd suggest the URLEncode instead... otherwise you'll get& in the file name. By URLEncoding it, you get the %XX where XX is the ascii code (for instance a space comes out as %20). the browser & client should be able to sort it out from there.

-tg

[szlamany]

@pradeep - I see the initial pop up has the D underlined - which is what a
& character would do to a string - that stinks.

but you are seeing the & character in the actual filename.

What version of IE

[szlamany]

BTW how big are your files? Why do you need to read/write in chunks?

They are huge - we do multi GB uploads and downloads

[Pradeep1210]

@pradeep - I see the initial pop up has the D underlined - which is what a
& character would do to a string - that stinks.

but you are seeing the & character in the actual filename.

What version of IE

IE Version is: 6.0

Yep. That underscore appearing there looks like a bug to me. Maybe it has been fixed in the latter versions of IE, but I'm not sure. I never use it other than development work.

[Pradeep1210]

They are huge - we do multi GB uploads and downloads

OK. Then it makes a lot of sense to transfer file in chunks, otherwise just a handful of users can eat up all the server memory and maybe crash your server too.

[szlamany]

OK. Then it makes a lot of sense to transfer file in chunks, otherwise just a handful of users can eat up all the server memory and maybe crash your server too.

Which is exactly what was happening!