Download Multiple Files in a Single Archive

Updated on Apr 30, 2026

Environment

Product

Telerik WebForms ZipLibrary for ASP.NET AJAX

Description

This sample demonstrates how to download multiple files from various formats within a single .zip archive by making use of the ZipLibrary. In order to use this zip library, you can include the required assemblies as explained in the Included Assemblies article.

You can find the original more advanced version of this implementation in the RadZipLibrary demo.

Important: Breaking Change in 2024 Q1

Starting with the 2024 Q1 release, the ZipArchive constructors have been made obsolete and are no longer accessible. You must use the new static factory methods instead:

Old Constructor	New Factory Method
new ZipArchive(stream, ZipArchiveMode.Create, ...)	ZipArchive.Create(stream)
new ZipArchive(stream, ZipArchiveMode.Read, ...)	ZipArchive.Read(stream)
new ZipArchive(stream, ZipArchiveMode.Update, ...)	ZipArchive.Update(stream)

Additionally, the ZipArchiveEntry must be wrapped in a using statement to ensure the entry is properly finalized. The BinaryWriter should not be wrapped in its own using block — instead, call writer.Flush() before the entry is disposed. Failing to follow this pattern results in a corrupt archive where all file entries show 0 bytes.

Solution

Suppose you have several files in a folder, each of different type (.png, .gif, .pdf, etc.). By clicking on the Download All Files button, we'll create a ZipArchiveEntry for each file, which will be responsible for adding the files to the archive.

ASP.NET

<telerik:RadButton ID="RadButton1" runat="server"
    Text="Download All Files" OnClick="RadButton1_Click">
    <Icon PrimaryIconCssClass="rbDownload" />
</telerik:RadButton>

C#

protected void RadButton1_Click(object sender, EventArgs e)
{
    MemoryStream memStream = new MemoryStream();
    using (ZipArchive archive = ZipArchive.Create(memStream))
    {
        string path = HttpContext.Current.Server.MapPath("~/Files");

        foreach (string docFile in Directory.GetFiles(path))
        {
            string fileName = Path.GetFileName(docFile);

            using (ZipArchiveEntry entry = archive.CreateEntry(fileName))
            {
                BinaryWriter writer = new BinaryWriter(entry.Open());
                writer.Write(File.ReadAllBytes(docFile));
                writer.Flush();
            }
        }
    }

    SendZipToClient(memStream);
}

private void SendZipToClient(MemoryStream memStream)
{
    memStream.Seek(0, SeekOrigin.Begin);

    if (memStream != null && memStream.Length > 0)
    {
        Response.Clear();
        Response.AddHeader("content-disposition", "attachment; filename=files.zip");
        Response.ContentType = "application/zip";
        Response.BinaryWrite(memStream.ToArray());
        Response.End();
    }
}

VB

Protected Sub RadButton1_Click(sender As Object, e As EventArgs)
    Dim memStream As New MemoryStream()
    Using archive As ZipArchive = ZipArchive.Create(memStream)
        For Each docFile As String In Directory.GetFiles(HttpContext.Current.Server.MapPath("~/Files"))
            Dim fileName As String = Path.GetFileName(docFile)
            Using entry As ZipArchiveEntry = archive.CreateEntry(fileName)
                Dim writer As New BinaryWriter(entry.Open())
                writer.Write(File.ReadAllBytes(docFile))
                writer.Flush()
            End Using
        Next
    End Using

    SendZipToClient(memStream)
End Sub

Private Sub SendZipToClient(memStream As MemoryStream)
    memStream.Seek(0, SeekOrigin.Begin)

    If memStream IsNot Nothing AndAlso memStream.Length > 0 Then
        Response.Clear()
        Response.AddHeader("content-disposition", "attachment; filename=files.zip")
        Response.ContentType = "application/zip"
        Response.BinaryWrite(memStream.ToArray())
        Response.[End]()
    End If
End Sub