Arshya Arshya - 2 months ago 39
C# Question

Creating Zip Files from Memory Stream C#

Basically the user should be able to click on one link and download multiple pdf files. But the Catch is I cannot create files on server or anywhere. Everything has to be in memory.

I was able to create memory stream and Response.Flush() it as pdf but how do I zip multiple memory streams without creating files.

Here is my code:

Response.ContentType = "application/zip";

// If the browser is receiving a mangled zipfile, IIS Compression may cause this problem. Some members have found that
// Response.ContentType = "application/octet-stream" has solved this. May be specific to Internet Explorer.
Response.AppendHeader("content-disposition", "attachment; filename=\"Download.zip\"");
Response.CacheControl = "Private";
Response.Cache.SetExpires(DateTime.Now.AddMinutes(3)); // or put a timestamp in the filename in the content-disposition

byte[] abyBuffer = new byte[4096];

ZipOutputStream outStream = new ZipOutputStream(Response.OutputStream);

outStream.SetLevel(3);

#region Repeat for each Memory Stream
MemoryStream fStream = CreateClassroomRoster();// This returns a memory stream with pdf document

ZipEntry objZipEntry = new ZipEntry(ZipEntry.CleanName("ClassroomRoster.pdf"));

objZipEntry.DateTime = DateTime.Now;

objZipEntry.Size = fStream.Length;

outStream.PutNextEntry(objZipEntry);

int count = fStream.Read(abyBuffer, 0, abyBuffer.Length);

while (count > 0)
{
outStream.Write(abyBuffer, 0, count);

count = fStream.Read(abyBuffer, 0, abyBuffer.Length);

if (!Response.IsClientConnected)
{
break;
}

Response.Flush();
}

fStream.Close();
#endregion

outStream.Finish();
outStream.Close();

Response.Flush();
Response.End();


This creates a zip file but there's no file inside it

I am using
using iTextSharp.text - for creating pdf
using ICSharpCode.SharpZipLib.Zip - for Zipping

Thanks,
Kavita

Answer

This link describes how to create a zip from a MemoryStream using SharpZipLib: https://github.com/icsharpcode/SharpZipLib/wiki/Zip-Samples#wiki-anchorMemory. Using this and iTextSharp, I was able to zip multiple PDF files that were created in memory.

Here is my code:

        MemoryStream outputMemStream = new MemoryStream();
        ZipOutputStream zipStream = new ZipOutputStream(outputMemStream);

        zipStream.SetLevel(3); //0-9, 9 being the highest level of compression
        byte[] bytes = null;

        // loops through the PDFs I need to create
        foreach (var record in records)
        {
            var newEntry = new ZipEntry("test" + i + ".pdf");
            newEntry.DateTime = DateTime.Now;

            zipStream.PutNextEntry(newEntry);

            bytes = CreatePDF(++i);

            MemoryStream inStream = new MemoryStream(bytes);
            StreamUtils.Copy(inStream, zipStream, new byte[4096]);
            inStream.Close();
            zipStream.CloseEntry();

        }

        zipStream.IsStreamOwner = false;    // False stops the Close also Closing the underlying stream.
        zipStream.Close();          // Must finish the ZipOutputStream before using outputMemStream.

        outputMemStream.Position = 0;

        return File(outputMemStream.ToArray(), "application/octet-stream", "reports.zip");

The CreatePDF Method:

private static byte[] CreatePDF(int i)
    {
        byte[] bytes = null;
        using (MemoryStream ms = new MemoryStream())
        {
            Document document = new Document(PageSize.A4, 25, 25, 30, 30);
            PdfWriter writer = PdfWriter.GetInstance(document, ms);
            document.Open();
            document.Add(new Paragraph("Hello World " + i));
            document.Close();
            writer.Close();
            bytes = ms.ToArray();
        }
        return bytes;

    }
Comments