Easily Zip / Unzip Files using Windows Shell32

(NOTE: The code has been updated for better compatibility on Windows Vista and 8.)

Introduction

If you want to zip / unzip files and folders without using third-party libraries, and you need a simple way to do it, then the Windows Shell32 is your choice.

The code is written with Visual Basic 2010 using .NET Framework 2.0 (running on Windows 7 x64), but it's simple and can be easily converted to any other language (like C#).

The Code

The first step is to create an empty ZIP file. Then, by using the CopyHere method, the files can be copied (or compressed) into the ZIP file. Also, using the same method, we can copy (or extract) the compressed files.

Public Class Form1
 
    Dim outputZip As String = "output zip file path"
    Dim inputZip As String = "input zip file path"
    Dim inputFolder As String = "input folder path"
    Dim outputFolder As String = "output folder path"
    
    'Declare the shell object
    Dim shObj As Object = Activator.CreateInstance(Type.GetTypeFromProgID("Shell.Application"))

    Sub Zip()

        'Lets create an empty Zip File .
        'The following data represents an empty zip file.
        Dim startBytes() As Byte = {80, 75, 5, 6, 0, 0, 0, 0, 0, 0, 0, _
                                     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
        'Data for an empty zip file.

        FileIO.FileSystem.WriteAllBytes(outputZip, startBytes, False)
        'We have successfully created the empty zip file.

        'Declare the folder which contains the items (files/folders) that you want to zip.
        Dim input As Object = shObj.NameSpace((inputFolder))

        'Declare the created empty zip file.
        Dim output As Object = shObj.NameSpace((outputZip))

        'Compress the items into the zip file.
        output.CopyHere((input.Items), 4)

    End Sub

    Sub UnZip()

        'Create directory in which you will unzip your items.
        IO.Directory.CreateDirectory(outputFolder)

        'Declare the folder where the items will be extracted.
        Dim output As Object = shObj.NameSpace((outputFolder))

        'Declare the input zip file.
        Dim input As Object = shObj.NameSpace((inputZip))

        'Extract the items from the zip file.
        output.CopyHere((input.Items), 4)

    End Sub
 
End Class

In the CopyHere method, option 4 was used, but it seems that it's actually ignored. Please refer to this page for more details: http://msdn.microsoft.com/en-us/library/windows/desktop/bb787866(v=vs.85).aspx.

Note that when using the methods NameSpace and CopyHere, the parameters were passed through additional parentheses. For some reason, it seems that there's a problem passing the variables themselves, therefore, the parentheses were used to pass "New" parameters which are created from and equivalent to the original ones. Otherwise, you would receive errors.

(Thanks to Thomas Tsigkonis for reporting the issues he faced on Windows 8.)

For those wondering if this method also compresses files (reduces their size): Yes! It does.

Also, you need to know that since the zipping/unzipping operations are carried-out by the Shell32 itself, you do not have a direct control on them. But, there are couple of ways to monitor the process, some of them are mentioned in the comments below.

At the end, this is an easy and fast-to-implement method for adding zipping / unzipping capabilities to your Windows application.

Best regards!