Decompress Zip files with Windows Shell API and C#

• Download demo project - 52.4 Kb

Introduction

With this code you can use the Windows Shell API in C# to decompress Zip files and do so without having to show the Copy Progress window shown above. Normally when you use the Shell API to decompress 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'.

Background

Ever needed to decompress 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 decompress 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 decompress folder hierarchies.

Using the code

The following code shows how to use the Windows Shell API to decompress a Zip file. The source folder points to a Zip file. The destination folder points to an output folder. This code as is will decompress 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'.

Shell32.ShellClass sc = new Shell32.ShellClass();
Shell32.Folder SrcFlder = sc.NameSpace(strSrcPath);
Shell32.Folder DestFlder = sc.NameSpace(strDestPath);
Shell32.FolderItems items = SrcFlder.Items();
DestFlder.CopyHere(items, 20);

The sample solution included with this article shows how to put this code into a console application and then launch this console app to decompress 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 decompress.

private void btnUnzip_Click(object sender, System.EventArgs e)
{
    System.Diagnostics.ProcessStartInfo i = new 
      System.Diagnostics.ProcessStartInfo(
      AppDomain.CurrentDomain.BaseDirectory + "unzip.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 + "\"";
    }
    else
    {
        args += txtSource.Text;
    }

    if(txtDestination.Text.IndexOf(" ") != -1)
    {
        //we got a space in the path so wrap it in double qoutes
        args += " " + "\"" + txtDestination.Text + "\"";
    }
    else
    {
        args += " " + txtDestination.Text;
    }
    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);
    p.WaitForExit();
    MessageBox.Show("Complete");
}

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.