I've just finished a meeting about an issue we're having with our .NET components. Though I fully agree with our decision, it's very frustrating, and I thought I'd share this with you.

A few years ago, before .NET was officially released, we decided to embrace the idea of digitally signing our ActiveX DLLs. The idea was to garantee our clients those DLLs were really from us. It was an added value that had no (visible) impact on the products themselves.

When .NET came in, though one could argue the strong name was sufficient, we decided to stick with digitally signing and do both. Actually, the strong name isn't offering CRL verification, nor detailed information about the "signer". It's not actual identity, it's only integrity.

Somewhere in time (we're still not sure when... maybe since .NET 1.0 SP3/.NET 1.1 SP1?), clients started complaining about our assemblies causing a network access. For most of them, the only impact was their sudden suspicion that our products were spywares, while in reality it was Windows' WinVerifyTrust API accessing crl.verisign.com or crl.thawte.com to check if the certificate used to sign the DLL was revoked.

But others got bigger problems. Some people behind a very strick firewall, ignoring outgoing connections instead of rejecting them, had a timeout while loading our assemblies. That timeout (at least 15 seconds) is hardcoded in WinVerifyTrust! We can't do anything about it.

And finally, those using a dial-up connection were seeing their Dial-Up dialog box appearing when our assemblies were loaded. Nothing to put confidence in our products. How come using Xceed Grid for .NET causes a network access?

There are solutions for those clients, but ugly solutions that either involve disabling CRL checking in the first place (yeah, right, let's sign our DLLs, then ask our clients to turn off its use!), or regularly install our certificate in the list of trusted certificates, which is only good for a certain period, and must be repeated again and again.

We've just decided to stop signing our .NET assemblies. Most of our competitors don't anyway. And those that do are having the same problem. But it's so damn frustrating to see that security is again loosing a battle. Sure, the impact is quite minor, but I'm left with a mixed feeling of failure and blames against the current implementation of WinVerifyTrust.

Found this through ComputerZen. The whole Richard Grimes incident is getting out of hands. Come on, people! Managed applications are the future. The .NET framework is awesome! I gave COM/ATL/ActiveX courses in the past. I could see those VB6 developers in front of me staring at the immensity of exceptions and rules and gotchas behind the COM scene. For the user, COM is great. But for the creator, it's an infinite loop of pitfalls.

"1199 signatories including 202 Microsoft MVPs since March 8th, 2005."

202? I can't beleive it.

Warning: Do not try this at home!

A few days ago, Pierre-Luc at support asked me if Xceed Zip for .NET was thread safe. I knew from his look that he was expecting a "yes" or a "no". At least, that's what the client who asked him the same question expected.

My first answer was more in nuances: Though the library was made to be safely accessible from multiple threads at the same time, by the nature of the sequential format of the zip file, it is not possible to work on the same zip file from multiple threads.

He nodded with approbation, confirming me his client wasn't trying such crazy action, but simply dealing with a multi-threaded application where each thread may be zipping in its own private file. I gave him my benediction: In that case, yes, Xceed Zip for .NET is thread safe.

Pierre-Luc wasn't two feet away when I was illuminated by an idea. It wouldn't be that crazy to try zipping into the same zip file from multiple threads. How neat would it be to benefit from multi processor or hyperthreading machines for zipping a single file? Guess what... you can! You shouldn't... but you can! Don't ask us to support this scenario... but you can!

Here's the deal. Any ZipArchive you modify gets updated when the last modify operation occurs. If you know you're about to make more than one modification to a single zip file, you should first call BeginUpdate, do all modifications, and finally call EndUpdate. The zip file will only get rebuilt on that final call. The files you copy into the zip file before EndUpdate will be compressed and stored in temp files within the ZipArchive's TempFolder.

That means any copy operation you perform within a BeginUpdate/EndUpdate block are atomic, and only involve compressing the sources into independant temp files. You see where I'm heading? How about spawning threads within that block, each thread copying its own source, and waiting for all threads to finish before calling EndUpdate?

I had to try it. I started with a class implementing IAsyncResult, which would be managing the copy operation on a separate thread:

But remember: Don't try this! I didn't tell you it was possible.

I had to take a look at an issue with a spanned zip file. The client graciously sent us the set of zip files he had on floppies. He copied each floppy in subfolders named "Disk1", "Disk2", "Disk3" and "Disk4", zipped those folders and sent us the resulting single huge zip file. Pretty standard.

I was about to copy each part back on floppies when I realized I was passing by a huge feature Xceed Zip for .NET offers regarding spanning and splitting: the ability to specify any AbstractFile, wherever it's located, when a new "disk" is required.

Before I show you how I skipped the unpleasant task of copying each part on separate floppies, let's first take a look at how you can support traditional spanning using Xceed Zip for .NET. The code below is what I call a minimum spanning implementation:

private static void Zip( AbstractFile zipFile, AbstractFolder sourceFolder )

{

  // Prepare ZipEvents object that will be passed to every method call.

  ZipEvents events = new ZipEvents();

  events.DiskRequired += new DiskRequiredEventHandler( ZipEvents_DiskRequired );

  // Create the target ZipArchive, and prepare for batch modifications.

  ZipArchive zip = new ZipArchive( events, null, zipFile );

  zip.BeginUpdate( events, null );

  try

  {

    // Allow this zip file to span.

    zip.AllowSpanning = true;

    // Zip this folder's contents

    sourceFolder.CopyFilesTo( events, null, zip, true, true );

  }

  finally

  {

    // Complete the batch modification of this zip file.

    zip.EndUpdate( events, null );

    events.DiskRequired -= new DiskRequiredEventHandler( ZipEvents_DiskRequired );

  }

}

private static void Unzip( AbstractFile zipFile, AbstractFolder destFolder )

{

  // Prepare ZipEvents object that will be passed to every method call.

  ZipEvents events = new ZipEvents();

  events.DiskRequired += new DiskRequiredEventHandler( ZipEvents_DiskRequired );

  // Create the source ZipArchive.

  ZipArchive zip = new ZipArchive( events, null, zipFile );

  try

  {

    // Unzip to destination folder.

    zip.CopyFilesTo( events, null, destFolder, true, true );

  }

  finally

  {

    events.DiskRequired -= new DiskRequiredEventHandler( ZipEvents_DiskRequired );

  }

}

private static void ZipEvents_DiskRequired(object sender, DiskRequiredEventArgs e)

{

  // Let the user know we need that disk and wait for feedback.

  Console.WriteLine( "Please insert disk #{0}, then press .", 
    e.DiskNumber.ToString() );

  Console.ReadLine();

  e.Action = DiskRequiredAction.Continue;

}

It's pretty straightforward. You simply give the user the time to insert the required disk. Don't forget that when unzipping, you must make sure the last zip file is the one available before creating your ZipArchive around it. There is no "insert last disk" event with Xceed Zip for .NET.

Now, back to my task. If you take a look at the DiskRequiredEventArgs parameter of the DiskRequired event, you see it exposes a "ZipFile" property of type AbstractFile. That's the AbstractFile for the part it's trying to locate. The above implementation requires a pause, to give time to the user to insert the correct disk. But what if the correct zip part is already available somewhere else? How about this implementation:

private static void ZipEvents_DiskRequired(object sender, DiskRequiredEventArgs e)

{

  // Let's check if the current zip file is located in a "DiskN" subfolder

  AbstractFolder subfolder = e.ZipFile.ParentFolder;

  if(  ( !subfolder.IsRoot )

    && ( subfolder.Name.ToUpper().StartsWith( "DISK" ) ) )

  {

    subfolder = subfolder.ParentFolder.GetFolder( 
      "Disk" + e.DiskNumber.ToString() );

    if( subfolder.Exists )

    {

      AbstractFile newZipFile = subfolder.GetFile( e.ZipFile.Name );

      if( newZipFile.Exists )

      {

        // No need to ask the user for the correct zip part, we found it!

        e.ZipFile = newZipFile;

        e.Action = DiskRequiredAction.Continue;

      }

    }

  }

  if( e.Action != DiskRequiredAction.Continue )

  {

    // Let the user know we need that disk and wait for feedback.

    Console.WriteLine( "Please insert disk #{0}, then press .", 
      e.DiskNumber.ToString() );

    Console.ReadLine();

    e.Action = DiskRequiredAction.Continue;

  }

}

As you can see, I have full control on what AbstractFile I provide to the library as the N^th zip file part. Since I have unzipped my client's zip file parts in my "D:\temp" folder, I can now call my Unzip method like this:

Unzip( 

  new DiskFile( @"d:\temp\Disk4\test.zip" ), 

  new DiskFolder( @"d:\temp\Unzipped" ) );

Then, the obvious striked me! Why did I unzip his "Floppies.zip" zip file in my "D:\temp" folder??? It's even simpler than I thought:

Unzip( 

  new ZippedFile( new DiskFile( @"d:\temp\floppies.zip" ), @"\Disk4\test.zip" ), 

  new DiskFolder( @"d:\temp\Unzipped" ) );

I'm unzipping zip file parts stored in a single zip file, without the need to have those parts really on floppies or even on disk. Wow! Files are files, folders are folders, no matter where they reside. Are you starting to get the idea behind the FileSystem?

A new Mono release today! As usual, I uninstall the previous release, install the new one, and test a few Xceed Zip for .NET console samples. Works perfectly!

But today I decided to try my Xceed FileSystem-based Command Prompt under Mono. Wow! Everything works almost perfectly. Zip, Ftp, Ram drive. Only a glitch with the Isolated Storage. This sample uses Mentalis.org's ConsoleAttributes library to customize the look and feel of the console. It works perfectly well with Mono (on Windows).

Any Mono users out there using Xceed products?

I'm playing with Google Maps, and it's amazingly easy to use and so well implemented. Dragging the map, pop-up balloons, directions, searching in a free textbox.

Here's Xceed Software. Here's the path I take every morning and evening.

Great job, Google!

I've been working part time (translation: I should be working on something else) on a new sample: my own Command Prompt. I know, I'm reinventing the wheel, not to count that Microsoft will launch a new one called msh (codename Monad). But it was more a concept or proof around exposing AbstractFolder and AbstractFile within a command prompt.

E:\>dir

  Directory of E:\

      DATE     TIME     SIZE or TYPE NAME
27/12/2004  4:23 PM         [FOLDER] Backup
03/11/2004 10:33 AM         [FOLDER] Chart30
24/11/2004 10:09 AM         [FOLDER] CLR Profiler
11/01/2005  5:24 PM         [FOLDER] Config.Msi
24/11/2004 10:10 AM         [FOLDER] My Music
12/01/2005  4:13 PM         [FOLDER] My Pictures
10/09/2004  1:52 PM         [FOLDER] RECYCLER
30/09/2004  8:40 PM         [FOLDER] System Volume Information
02/02/2005  2:49 PM         [FOLDER] temp
03/11/2004 10:33 AM         [FOLDER] XceedProjectsNET
25/01/2005  7:06 AM              143 toto.txt

  Files: 1  Folders: 14  Total file size: 143

E:\>copy toto.txt temp
 100%
E:\>cd temp
E:\temp\>

As you can see, I can list the contents of folders, copy files, and change the working folder. The application simply manages a working "AbstractFolder", and enables commands to act on that folder (or an AbstractFolder obtained from an absolute path).

The sample quicky evolved into a prototype for upcoming features. Among other things, I needed a way to recognize a path like "E:\temp\test.zip\images" as a ZippedFolder within a zip file. Let's stop the talking, and show some traces:

E:\temp\>md test.zip
E:\temp\>md test.zip\images
E:\temp\>copy "..\My Pictures\Chalet\*" test.zip\images
 100%
E:\temp\>

What have I done here? Create a folder named "test.zip"? Well, the "md" command recognized the ".zip" extension as a request to create a new empty zip file. The second "md" command actually created a new folder within the zip file. And the paths can freely use the zip filename as a folder part for any command, as shown with the copy example. If we display the contents of "E:\temp", we see the two expected files:

E:\temp\>dir

  Directory of E:\temp\

      DATE     TIME     SIZE or TYPE NAME
02/02/2005  3:00 PM         40068736 test.zip
25/01/2005  7:06 AM              143 toto.txt

  Files: 2  Folders: 0  Total file size: 40068879

E:\temp\>

As you can see, "test.zip" is really a file (DiskFile) within "E:\temp" (DiskFolder). What happens if I try changing the current folder into that zip file?

E:\temp\>cd test.zip
E:\temp\test.zip\>dir

  Directory of E:\temp\test.zip\

      DATE     TIME     SIZE or TYPE NAME
02/02/2005  3:00 PM         [FOLDER] images

  Files: 0  Folders: 1  Total file size: 0

E:\temp\test.zip\>cd images
E:\temp\test.zip\images\>dir

  Directory of E:\temp\test.zip\images\

      DATE     TIME     SIZE or TYPE NAME
06/08/2000  4:40 PM          6400006 Chaises.bmp
06/08/2000  4:35 PM          6348550 Chute.bmp
06/08/2000  4:29 PM          6337678 Ciel1.bmp
06/08/2000  4:30 PM          6396226 Ciel2.bmp
06/08/2000  4:33 PM          6414418 Ciel3.bmp
06/08/2000  4:38 PM          6524278 Couple.bmp
06/08/2000  4:37 PM          6388054 Martine.bmp
06/08/2000  4:32 PM          6405478 Ombre.bmp
06/08/2000  4:41 PM          6359254 Rochers.bmp

  Files: 9  Folders: 0  Total file size: 57573942

E:\temp\test.zip\images\>

The zip file is exposed as a folder, because the path "E:\temp\test.zip" was recognized and mapped to a ZippedFolder around a DiskFile. And "images" is nothing more than a subfolder within that root ZippedFolder, actually something like:

new ZippedFolder( new DiskFile( @"E:\temp\test.zip" ), @"\images" );

Ok, let's get into serious things:

E:\temp\test.zip\images\>cd ..\..
E:\temp\>copy *.zip RAM:\
 100%
E:\temp\>cd RAM:\test.zip\images
RAM:\test.zip\images\>dir m*.bmp

  Directory of RAM:\test.zip\images\

      DATE     TIME     SIZE or TYPE NAME
06/08/2000  4:37 PM          6388054 Martine.bmp

  Files: 1  Folders: 0  Total file size: 6388054

RAM:\test.zip\images\>

My Command Prompt exposes a root MemoryFolder called "RAM:\", which I can freely use. The commands act the same, no matter if I'm deeling with a ZippedFolder around a DiskFile or a MemoryFile. Want more?

RAM:\test.zip\images\>cd ftp://vermouth
ftp://vermouth\>dir

  Directory of ftp://vermouth\

      DATE     TIME     SIZE or TYPE NAME

  Files: 0  Folders: 0  Total file size: 0

ftp://vermouth\>md foobar.zip
ftp://vermouth\>copy "E:\My Music\WMA\Mes Aieux" foobar.zip
 100%
ftp://vermouth\>dir

  Directory of ftp://vermouth\

      DATE     TIME     SIZE or TYPE NAME
02/02/2005  3:20 PM         62936759 foobar.zip

  Files: 1  Folders: 0  Total file size: 62936759

ftp://vermouth\>dir c:\inetpub\ftproot

  Directory of c:\inetpub\ftproot\

      DATE     TIME     SIZE or TYPE NAME
02/02/2005  3:20 PM         62936759 foobar.zip

  Files: 1  Folders: 0  Total file size: 62936759

ftp://vermouth\>

FTP servers are threated as any other kind of AbstractFolder. The application simply recognize the "FTP:" prefix as a signature for a root FtpFolder, as it did with "RAM:" exposed as a MemoryFolder. The command implementations don't care what kind of AbstractFolder or AbstractFile they are dealing with.

The engine behind this involves FileSystemMapper-derived classes. They mainly get asked two kinds of questions:

Question 1: Do you recognize this path as a root?

If so, they remove the part of the path they could recognize as a root folder, and return the matching AbstractFolder.

Examples of mappers and their responsability:

• DiskMapper : Drive letters and UNC paths (yes, you can "cd" into a UNC path!)
• FtpMapper : The "FTP:" prefix with server name, and optional username and password (e.g. ftp://user:pass@vermouth:9999)
• IsolatedStorageMapper : A custom prefix name like "STORE:" (that's the one my sample app supports).
• MemoryMapper : A custom prefix used to create the initial root MemoryFolder, like "RAM:" (that's the one my app supports). You can create more than one MemoryMapper to have more than one ram drive.

Question 2: Can you represent this AbstractFile as an AbstractFolder?

If so, they simply return the matching AbstractFolder.

An example of such a mapper:

• ZipFileMapper : It simply checks if the provided AbstractFile exists, then tries to create a ZipArchive around that AbstractFile in a try/catch. If it succeeds, it returns this ZipArchive (which derives from ZippedFolder).

Curiously, today I came across a post on our forums asking how to detect if a file is really a zip file. I gave this man the "new ZipArchive within a try/catch" solution, and he came back, as I feared, with concerns with the time wasted catching an exception for all those non-zip files. It's actually one of the bottlenecks of my Command Prompt sample. A lot of time is wasted throwing an exception for all non-zip files my app comes across. Well, I guess I'll have to work sooner than later on a new "ZipArchive.IsZipFile" method!

Now, you have to convince my boss I should put more time on this sample and these new FileSystem features! Does mapping absolute paths like shown above to their proper AbstractFolder or AbstractFile something that could be usefull for you?