How to download an image file as a Zip file using C# and J#

• Download source code - 348 KB

Introduction

Recently, I had to build a club website where the user has the ability to download an image as a zip file. So, I planned to make a procedure which will automatically convert an image file to a zip file. Online search led me to a blog with this wonderful idea of using the ZIP option in J#, and it really attracted me.

Background

In this article, I will explain the usage of ZIP functionality in J# from C# code. The code in this application has been designed to reuse in a copy-paste fashion and not as a library.

This application consumes J# classes internally. For this, we must first refer to the J# .NET library. Physically, it resides as a file named vjslib.dll. If you are not very sure how to refer to a library in your project, please follow the steps below:

Right click your project in Server Explorer and click on "Add Reference" -> select the .NET tab -> scroll down and select "vjslib" -> click OK and you are there. Now, you can refer the Java library classes within your application.

using java.util;
using java.util.zip;
using java.io;

The java.util.zip namespace contains the classes and methods to implement the compress and uncompress functionalities. The main classes used from the above namespaces are

• ZipFile
• ZipEntry
• ZipOutputSteam
• Enumeration

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;
using java.util;
using java.util.zip;
using java.io;
public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }
    protected void lnkImage_Click(object sender, EventArgs e)
    {
       string FilePath = Server.MapPath("~/Image/");
       string FileDest = Server.MapPath("~/Image/");
       Zip(FileDest + "test.zip", FilePath + "Download_File_As_Zip_File/pic.jpg");
    }
    private void Zip(string zipFileName, string sourceFile)
    {
        FileOutputStream filOpStrm = new FileOutputStream(zipFileName);
        ZipOutputStream zipOpStrm = new ZipOutputStream(filOpStrm);
        FileInputStream filIpStrm = null;
        filIpStrm = new FileInputStream(sourceFile);
        ZipEntry ze = new ZipEntry(Path.GetFileName(sourceFile));
        zipOpStrm.putNextEntry(ze);
        sbyte[] buffer = new sbyte[1024];
        int len = 0;
        while ((len = filIpStrm.read(buffer)) >= 0)
        {
            zipOpStrm.write(buffer, 0, len);
        }

        zipOpStrm.closeEntry();
        filIpStrm.close();
        zipOpStrm.close();
        filOpStrm.close();
        FileInfo file = new FileInfo(zipFileName); 
        Response.ClearHeaders();
        Response.ClearContent();
        Response.ContentType = "application/octet-stream";
        Response.AddHeader("Content-Disposition", 
          "attachment; filename=" + "test.zip");
        Response.WriteFile(file.FullName);
        Response.End();
    }
    protected void lnkSource_Click(object sender, EventArgs e)
    {
        //Downloadzip.zip
        FileInfo file = new FileInfo(Server.MapPath("~/Image/") + 
                                     "Downloadzip.zip");
        Response.ClearHeaders();
        Response.ClearContent();
        Response.ContentType = "application/octet-stream";
        Response.AddHeader("Content-Disposition", 
          "attachment; filename=" + "Downloadzip.zip");
        Response.WriteFile(file.FullName);
        Response.End();
    }
}