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context.Response.Write MemoryStream

Posted on 2010-08-17
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Last Modified: 2012-05-10
Good afternoon,
Ive written a simple Handeler page, which I hoped would be able to get the user to download a ZIP file without having save the file on the hard drive.

Im using the Ionic.zip extension from http://dotnetzip.codeplex.com/, which creates a zip file.

The zip file creation seems to work fine, and after the line "myZipFile.Save("C:\New folder (2)\outSig.zip")" is run, I can see the zip file and open it fine if I comment out the following lines:-

        Dim outStream As New MemoryStream
        myZipFile.Save(outStream)
        context.Response.Write(outStream)

If I run with the above lines uncommented then the page failes saying:-
Invalid at the top level of the document. Error processing resource 'http://localhost:58053/Handler1.ashx'. Line 1, Positi...

System.IO.MemoryStream
^


Any ideas what Im doing wrong with the:-
        Dim outStream As New MemoryStream
        myZipFile.Save(outStream)
        context.Response.Write(outStream)

Any help would be appriciated.

Thank you
Imports System.IO
Imports Ionic.Zip

Public Class Handler1
    Implements System.Web.IHttpHandler

    Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest

        context.Response.ContentType = "application/zip"

        Dim myZipFile As New ZipFile

        Dim strText As String = "This is some sample text"


        myZipFile.AddEntry("default.htm", "\", strText)

        myZipFile.AddFile(context.Request.PhysicalApplicationPath & "logos\myLogo.jpg", "\")

        Dim outStream As New MemoryStream

        myZipFile.Save(outStream)

        context.Response.Write(outStream)
    End Sub
End Class

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Question by:tonelm54
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Accepted Solution

by:
Bob Learned earned 500 total points
ID: 33454605
The preferred method, with ASP.NET, is to write to the OutputStream.

HttpResponse.OutputStream Property
http://msdn.microsoft.com/en-us/library/system.web.httpresponse.outputstream.aspx

<%@ Page Language="VB" %>
<%@ import Namespace="System.Drawing" %>
<%@ import Namespace="System.Drawing.Imaging" %>
<%@ import Namespace="System.Drawing.Drawing2D" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

   Private Sub Page_Load(sender As Object, e As EventArgs)
      ' Set the page's content type to JPEG files
      ' and clears all content output from the buffer stream.
      Response.ContentType = "image/jpeg"
      Response.Clear()

      ' Buffer response so that page is sent
      ' after processing is complete.
      Response.BufferOutput = True

      ' Create a font style.
      Dim rectangleFont As New Font( _
          "Arial", 10, FontStyle.Bold)

      ' Create integer variables.
      Dim height As Integer = 100
      Dim width As Integer = 200

      ' Create a random number generator and create
      ' variable values based on it.
      Dim r As New Random()
      Dim x As Integer = r.Next(75)
      Dim a As Integer = r.Next(155)
      Dim x1 As Integer = r.Next(100)

      ' Create a bitmap and use it to create a
      ' Graphics object.
      Dim bmp As New Bitmap( _
          width, height, PixelFormat.Format24bppRgb)
      Dim g As Graphics = Graphics.FromImage(bmp)

      g.SmoothingMode = SmoothingMode.AntiAlias
      g.Clear(Color.LightGray)

      ' Use the Graphics object to draw three rectangles.
      g.DrawRectangle(Pens.White, 1, 1, width - 3, height - 3)
      g.DrawRectangle(Pens.Aquamarine, 2, 2, width - 3, height - 3)
      g.DrawRectangle(Pens.Black, 0, 0, width, height)

      ' Use the Graphics object to write a string
      ' on the rectangles.
      g.DrawString("ASP.NET Samples", rectangleFont, SystemBrushes.WindowText, New PointF(10, 40))

      ' Apply color to two of the rectangles.
      g.FillRectangle( _
          New SolidBrush( _
              Color.FromArgb(a, 255, 128, 255)), _
          x, 20, 100, 50)

      g.FillRectangle( _
          New LinearGradientBrush( _
              New Point(x, 10), _
              New Point(x1 + 75, 50 + 30), _
              Color.FromArgb(128, 0, 0, 128), _
              Color.FromArgb(255, 255, 255, 240)), _
          x1, 50, 75, 30)

      ' Save the bitmap to the response stream and
      ' convert it to JPEG format.
      bmp.Save(Response.OutputStream, ImageFormat.Jpeg)

      ' Release memory used by the Graphics object
      ' and the bitmap.
      g.Dispose()
      bmp.Dispose()

      ' Send the output to the client.
      Response.Flush()
   End Sub 'Page_Load

</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>ASP.NET Example</title>
</head>
<body>
    <form id="form1" runat="server">
    </form>
</body>
</html>

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