Introduction

In this post I am explain how to Download multiple files as ZIP at once using ASP.NET & C#.

Here I have used ICSharpCode.SharpZipLib.dll to Create ZIP file.

Steps :

Step - 1: Create New Project.

Go to File > New > Project > Select asp.net web forms application > Entry Application Name > Click OK.

Step-2: Add a Class.

Right Click on Solution Explorer > Add > Class > Enter Class Name > Add.
Here is the class.

namespace ASPDownloadMultiFile
{
    public class MyFile
    {
        public string FileName { get; set; }
        public string FilePath { get; set; }
        public decimal FileSize { get; set; }
    }
}
        

Step-3: Add New Folder.

Right Click on Solution Explorer > Add > New Folder > Rename Folder.

Step-4: Add a Webpage and Design for Show files.

Go to Solution Explorer > Right Click on Project name form Solution Explorer > Add > New item > Select web form/ web form using master page under Web > Enter page name > Add.

HTML Code

    <h3>Multiple file download at a time using asp.net.</h3>
    <div>
        <%-- This is for show Downloadable Files --%>
        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false">
            <Columns>
                <asp:BoundField HeaderText="File Name" DataField="FileName" />
                <asp:BoundField HeaderText="File Size (KB)" DataField="FileSize" />
                <asp:TemplateField>
                    <ItemTemplate>
                        <a href='<%#Eval("FilePath") %>' target="_blank">Download</a>
                    </ItemTemplate>
                </asp:TemplateField>
            </Columns>
        </asp:GridView>
        <br />
        <asp:Button ID="btnDownloadAll" runat="server" Text="Download All Files as ZIP" OnClick="btnDownloadAll_Click" />
    </div>
        

Step-5: Write code into page load event for show data.

Write below code into Page_Load event for show files in Gridview.

         protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                PopulateFiles();
            }
        }        

         private void PopulateFiles()
        {
            DirectoryInfo DI = new DirectoryInfo(Server.MapPath("~/DownloadFolder"));
            List<MyFile> allFiles = new List<MyFile>();
            foreach (var i in DI.GetFiles())
            {
                allFiles.Add(new MyFile
                {
                     FileName = i.Name,
                      FilePath =  i.FullName.Replace(Server.MapPath("~/"),""), // For Get URL FORM Full Path
                       FileSize = i.Length/1024
                }
                );
            }
            GridView1.DataSource = allFiles;
            GridView1.DataBind();
        }        

Step-6: Add a Reference for Create ZIP.

Download ICSharpCode.SharpZipLib.dll
Right Click on References under solution explorar > Add Reference... > Browse > Select ICSharpCode.SharpZipLib.dll > Add > Ok.

Step-7: Write code for Download multiple files at once.

Write below code into button click event for download multiple files.

         protected void btnDownloadAll_Click(object sender, EventArgs e)
        {
            // Here we will create zip file & download
            string zipFileName = "MyZipFiles.zip";
            Response.ContentType = "application/zip";
            Response.AddHeader("content-disposition","fileName="+ zipFileName);
            byte[] buffer = new byte[4096];
            ZipOutputStream zipOutputStream = new ZipOutputStream(Response.OutputStream);
            zipOutputStream.SetLevel(3);
            try
            {
                DirectoryInfo DI = new DirectoryInfo(Server.MapPath("~/DownloadFolder"));
                foreach (var i in DI.GetFiles())
                {
                    Stream fs = File.OpenRead(i.FullName);
                    ZipEntry zipEntry = new ZipEntry(ZipEntry.CleanName(i.Name));
                    zipEntry.Size = fs.Length;
                    zipOutputStream.PutNextEntry(zipEntry);
                    int count = fs.Read(buffer, 0, buffer.Length);
                    while (count > 0)
                    {
                        zipOutputStream.Write(buffer, 0, count);
                        count = fs.Read(buffer, 0, buffer.Length);
                        if (!Response.IsClientConnected)
                        {
                            break;
                        }
                        Response.Flush();
                    }
                    fs.Close();
                }
                zipOutputStream.Close();
                Response.Flush();
                Response.End();
            }
            catch (Exception)
            {
                throw;
            }            
        }        

Step-8: Run Application.