ASP.NET Filename encoding while sending file - asp.net

Question

I am sending a file from ASP.NET Page to the browser. To properly send a filename I am adding a header:
Response.ContentType = "application/octet-stream";
Response.AddHeader("Content-Disposition", "attachment; filename=" + filename);
The problem is that when file contains white spaces (e.g. "abc def") browser receives only "abc" part of the filename. I have tried with: Server.HtmlEncode but it didn't help.
Do you have any idea how to solve this problem?
PK

Answer 1

Put the file name in quotes:-
Response.ContentType = "application/octet-stream";
Response.AddHeader("Content-Disposition", "attachment; filename=\"" + filename + "\"");

Answer 2

Don't UrlEncode. This is not the right way to escape a value for use in an HTTP structured header parameter. It only works in IE due to that browser's buggy handling, and even then not reliably.
For a space you can use a quoted-string as suggested by Anthony (+1). But the dirty truth of Content-Disposition is that there is no reliable, supported escaping scheme that can be used to put arbitrary characters such as ;, " or Unicode characters in the filename parameter. The only approach that works reliably cross-browser is to drop the filename parameter completely and put the desired filename in the URI as a trailing, UTF-8+URL-encoded path part.
See this answer for some background.

Answer 3

Filename with special symbols(e.g: space; # # ! $ ) or Non-Unicode characters either cannot be supported by some browsers or cause incorrect filename in client machine.
Here is an article by a Chinese called chanext, he gave a perfect way to solve this problem:
this article gave a sample code(written with c#) to show how to get perfect solution to this problem in the all four popular browsers (IE; Opera; Firefox and Chrome)
the filename "Microsoft.Asp.Net.doc" and "F ile;;!#%#^&y.doc" can both be output correctly using the way the author provided in this article.
http://ciznx.com/post/aspnetstreamdownloaddisplaynonunicodespacechar.aspx

Answer 4

Based on the code referenced by #chanext I cleaned it up and put it into a single extension method. Hope this can help someone.
Partial Class Uploader
Inherits Page
Private Sub UploadFile()
Dim sFileName As String
Dim oPdf As MigraDoc.Rendering.PdfDocumentRenderer
sFileName = "File Name With Spaces #22.pdf"
With Me.Request.Browser
If .Browser = "InternetExplorer" OrElse .Browser = "IE" Then
sFileName = sFileName.EncodeForIE
Else
sFileName = String.Format("""{0}""", sFileName)
End If
End With
oPdf = New MigraDoc.Rendering.PdfDocumentRenderer
oPdf.Document = FileFactory.CreatePdf()
oPdf.RenderDocument()
Using oStream As New MemoryStream
oPdf.Save(oStream, False)
Me.Response.Clear()
Me.Response.ContentType = "application/pdf"
Me.Response.AddHeader("content-disposition", String.Format("attachment; filename={0}", sFileName))
Me.Response.AddHeader("content-length", oStream.Length)
Me.Response.BinaryWrite(oStream.ToArray)
End Using
Me.Response.Flush()
Me.Response.End()
End Sub
End Class
Public Module StringExtensions
<Extension()>
Public Function EncodeForIE(Url As String) As String
Dim _
sReservedChars,
sEncodedString As String
sReservedChars = "$-_.+!*'(),#=&"
With New StringBuilder
Url.ToList.ForEach(Sub(C)
If Char.IsLetterOrDigit(C) OrElse sReservedChars.Contains(C) Then
.Append(C)
Else
With New StringBuilder
C.ToBytes.ToList.ForEach(Sub(B)
.AppendFormat("%{0}", Convert.ToString(B, 16))
End Sub)
sEncodedString = .ToString
End With
.Append(sEncodedString)
End If
End Sub)
Return .ToString
End With
End Function
<Extension()>
Public Function ToBytes(Chr As Char) As Byte()
Return Encoding.UTF8.GetBytes(Chr.ToString)
End Function
End Module