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Posted 24 Oct 2005


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Compress Zip files with Windows Shell API and C#

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24 Oct 2005Public Domain3 min read
Use Windows Shell API in C# to compress Zip files without showing the Copy Progress window.

Sample Image


This is a follow up article to the one that I wrote about decompressing Zip files. With this code you can use the Windows Shell API in C# to compress Zip files and do so without having to show the Copy Progress window shown above. Normally when you use the Shell API to compress a Zip file, it will show a Copy Progress window even when you set the options to tell Windows not to show it. To get around this, you move the Shell API code to a separate executable and then launch that executable using the .NET Process class being sure to set the process window style to 'Hidden'.


Ever needed to compress Zip files and needed a better Zip than what comes with many of the free compression libraries out there? I.e. you needed to compress folders and subfolders as well as files. Windows Zipping can compress more than just individual files. All you need is a way to programmatically get Windows to silently compress these Zip files. Of course you could spend $300 on one of the commercial Zip components, but it's hard to beat free if all you need is to compress folder hierarchies.

Using the code

The following code shows how to use the Windows Shell API to compress a Zip file. First you create an empty Zip file. To do this create a properly constructed byte array and then save that array as a file with a '.zip' extension. How did I know what bytes to put into the array? Well I just used Windows to create a Zip file with a single file compressed inside. Then I opened the Zip with Windows and deleted the compressed file. That left me with an empty Zip. Next I opened the empty Zip file in a hex editor (Visual Studio) and looked at the hex byte values and converted them to decimal with Windows Calc and copied those decimal values into my byte array code. The source folder points to a folder you want to compress. The destination folder points to the empty Zip file you just created. This code as is will compress the Zip file, however it will also show the Copy Progress window. To make this code work, you will also need to set a reference to a COM library. In the References window, go to the COM tab and select the library labeled 'Microsoft Shell Controls and Automation'.

//Create an empty zip file
byte[] emptyzip = new byte[]{80,75,5,6,0,0,0,0,0, 

FileStream fs = File.Create(args[1]);
fs.Write(emptyzip, 0, emptyzip.Length);
fs = null;

//Copy a folder and its contents into the newly created zip file
Shell32.ShellClass sc = new Shell32.ShellClass();
Shell32.Folder SrcFlder = sc.NameSpace(args[0]);
Shell32.Folder DestFlder = sc.NameSpace(args[1]); 
Shell32.FolderItems items = SrcFlder.Items();
DestFlder.CopyHere(items, 20);

//Ziping a file using the Windows Shell API 
//creates another thread where the zipping is executed.
//This means that it is possible that this console app 
//would end before the zipping thread 
//starts to execute which would cause the zip to never 
//occur and you will end up with just
//an empty zip file. So wait a second and give 
//the zipping thread time to get started

The sample solution included with this article shows how to put this code into a console application and then launch this console app to compress the Zip without showing the Copy Progress window.

The code below shows a button click event handler that contains the code used to launch the console application so that there is no UI during the compress:

private void btnUnzip_Click(object sender, System.EventArgs e)
    //Test to see if the user entered a zip file name
    if(txtZipFileName.Text.Trim() == "")
        MessageBox.Show("You must enter what" + 
               " you want the name of the zip file to be");
        //Change the background color to cue the user to what needs fixed
        txtZipFileName.BackColor = Color.Yellow;
        //Reset the background color
        txtZipFileName.BackColor = Color.White;

    //Launch the zip.exe console app to do the actual zipping
    System.Diagnostics.ProcessStartInfo i =
        new System.Diagnostics.ProcessStartInfo(
        AppDomain.CurrentDomain.BaseDirectory + "zip.exe");
    i.CreateNoWindow = true;
    string args = "";

    if(txtSource.Text.IndexOf(" ") != -1)
        //we got a space in the path so wrap it in double qoutes
        args += "\"" + txtSource.Text + "\"";
        args += txtSource.Text;

    string dest = txtDestination.Text;

    if(dest.EndsWith(@"\") == false)
        dest += @"\";

    //Make sure the zip file name ends with a zip extension
    if(txtZipFileName.Text.ToUpper().EndsWith(".ZIP") == false)
        txtZipFileName.Text += ".zip";

    dest += txtZipFileName.Text;

    if(dest.IndexOf(" ") != -1)
        //we got a space in the path so wrap it in double qoutes
        args += " " + "\"" + dest + "\"";
        args += " " + dest;

    i.Arguments = args;

    //Mark the process window as hidden so 
    //that the progress copy window doesn't show
    i.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;    
    System.Diagnostics.Process p = System.Diagnostics.Process.Start(i);

Points of Interest

  • It's free!
  • You can use Windows to create the Zip file instead of an expensive Zip library to work with folder hierarchies.
  • Works with or without showing the Copy Progress window.
  • Uses the Windows Shell API which has a lot of of interesting Windows integration possibilities.


This article, along with any associated source code and files, is licensed under A Public Domain dedication


About the Author

Gerald Gibson Jr
Web Developer
United States United States
I have been coding since 4th grade in elementary school back in 1981. I concentrate mainly on Microsoft technologies from the old MSDOS/MSBASIC to coding in VC++ then Visual Basic and now .Net. I try to stay on top of the trends coming from Microsoft such as the Millennium Project, Windows DNA, and my new favorite Windows clustering servers.

I have dabbled in making games in my initial VC++ days, but spent most of the past 10 years working on business apps in VB, C++, and the past 7 years in C#.

I eventually hope to get my own company supporting me so I can concentrate on my real dream of creating clusters of automated robots for use in various hazardous industries.

Comments and Discussions

GeneralOriginal code will not handle blank folders, minor fix solve that Pin
Kevin Eldon4-Apr-08 10:58
MemberKevin Eldon4-Apr-08 10:58 
GeneralRe: Original code will not handle blank folders, minor fix solve that Pin
Gerald Gibson Jr4-Apr-08 12:08
MemberGerald Gibson Jr4-Apr-08 12:08 
QuestionWhere is unzip.exe and zip.exe? Pin
Clutchplate31-Mar-08 5:17
MemberClutchplate31-Mar-08 5:17 
GeneralRe: Where is unzip.exe and zip.exe? Pin
Gerald Gibson Jr31-Mar-08 5:30
MemberGerald Gibson Jr31-Mar-08 5:30 
GeneralPassword Protected Pin
Shahzad.Aslam23-Dec-07 22:20
MemberShahzad.Aslam23-Dec-07 22:20 
GeneralRe: Password Protected Pin
RAllala13-Jun-12 3:21
MemberRAllala13-Jun-12 3:21 
General2 questions Pin
ania9-Dec-07 7:09
Memberania9-Dec-07 7:09 
Question2 Questions Pin
carlik20-Jun-07 7:09
Membercarlik20-Jun-07 7:09 
AnswerRe: 2 Questions Pin
Gerald Gibson Jr20-Jun-07 7:17
MemberGerald Gibson Jr20-Jun-07 7:17 
QuestionI don't see the "compress" statement Pin
Sean Z12-Jun-07 9:45
MemberSean Z12-Jun-07 9:45 
AnswerRe: I don't see the "compress" statement Pin
Gerald Gibson Jr12-Jun-07 12:02
MemberGerald Gibson Jr12-Jun-07 12:02 
GeneralExcellent Utility Pin
gss28-Mar-07 0:30
Membergss28-Mar-07 0:30 
GeneralRe: Excellent Utility Pin
Gerald Gibson Jr28-Mar-07 7:48
MemberGerald Gibson Jr28-Mar-07 7:48 
QuestionError Running Sample Pin
hqh5123-Feb-07 16:53
Memberhqh5123-Feb-07 16:53 
AnswerRe: Error Running Sample Pin
Gerald Gibson Jr23-Feb-07 16:55
MemberGerald Gibson Jr23-Feb-07 16:55 
QuestionRe: Error Running Sample Pin
hqh5123-Feb-07 17:13
Memberhqh5123-Feb-07 17:13 
AnswerRe: Error Running Sample Pin
Gerald Gibson Jr24-Feb-07 4:34
MemberGerald Gibson Jr24-Feb-07 4:34 
GeneralRe: Error Running Sample Pin
hqh5124-Feb-07 5:09
Memberhqh5124-Feb-07 5:09 
GeneralRe: Error Running Sample Pin
Gerald Gibson Jr24-Feb-07 5:12
MemberGerald Gibson Jr24-Feb-07 5:12 
GeneralThanks for this great piece of code Pin
IanRae3-Feb-07 5:04
MemberIanRae3-Feb-07 5:04 
GeneralRe: Thanks for this great piece of code [modified] Pin
Gerald Gibson Jr3-Feb-07 5:25
MemberGerald Gibson Jr3-Feb-07 5:25 
GeneralReliability is excellent Pin
Coach LazyEye8-Jan-07 8:59
MemberCoach LazyEye8-Jan-07 8:59 
GeneralRe: Reliability is excellent Pin
Gerald Gibson Jr9-Jan-07 4:49
MemberGerald Gibson Jr9-Jan-07 4:49 
GeneralI want to zip a single file rather than a folder this shell api supports this problem Pin
haneef111-Dec-06 18:36
Memberhaneef111-Dec-06 18:36 
GeneralRe: I want to zip a single file rather than a folder this shell api supports this problem Pin
Gerald Gibson Jr12-Dec-06 1:52
MemberGerald Gibson Jr12-Dec-06 1:52 

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