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	Win32FileFinder

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The following notes are taken from the source code documentation of the Win32FileFinder class.

A utility class that wraps the Win32 file finding functions in a familar and convenient managed way with callbacks while hiding the underlying complexities of the API calls, handles and return codes.

The .NET Framework methods in System.IO for finding files and folders perform a bulk operation and return arrays of FileInfo or DirectoryInfo objects. Callers can block for an unacceptably long time if large numbers of results are accumulated by methods like GetFiles or GetDirectories. These methods are not interruptible and the results are not available until the method completes.

This class uses the FindFirstFile, FindNextFile and FindClose Win32 API methods internally to run a find, sending an event with managed FileInfo or DirectoryInfo objects as callbacks so that consumers can work with the results as they are found. The caller sequentially consumes the results and can cancel the find during a callback, which is not possible with the managed methods.

The class does not yet recursively scan folders. This can be done, but it will be necessary to maintain a stack of the find handles.

I created the Win32FileFinder class after years of dissatisfaction with the standard GetFiles and GetDirectories methods. As the documentation above says, the standard managed methods block while the result arrays are being generated and cannot be interrupted. The block can be hidden by running it in a thread, but this adds irritating code complexity. Even worse, there is no way of getting progress from the standard methods, nor is there a way of interrupting them.

The Win32FileFinder class uses Win32 API calls and handles internally to run the file find process and it feeds the results sequentially back to the caller via an event. The class hides the internal workings from the caller who only sees familiar managed FileInfo and DirectoryInfo objects passed back in the event. The find process can be cancelled by setting a flag in the event arguments. Beginner .NET developers might be interested in the Interop techniques used with the unmanaged API calls and structures. The class also implements to the IDisposable interface to ensure that the underlying HANDLE is eventually closed.

I tried to make the class as easy as possible to use. This is the skeleton code of how to use the class:

finder = new Win32FileFinder();
finder.FileFound += new FileFoundEventHandler(finder_FileFound);
finder.Find(@"C:\windows\system32\win*");
:
private void finder_FileFound(object sender, FileFoundEventArgs e)
{
  if (e.File != null)
    Console.WriteLine("Found file: {0}", e.File.FullName);
  else
    Console.WriteLine("Found folder: {0}", e.Folder.FullName);
  // you could set e.Cancel=true here to stop finding
}

Following is a sample of the output of the test driver console command. The 2nd parameter is the maximum number of find results to process.

>finder C:\windows\system32\e* 20
050214161047 020129143310    64.0 KB C:\windows\system32\EBAPI.dll
050120152453 020711160600    80.0 KB C:\windows\system32\EBPEPS02.DLL
050120152453 010903170400  182 bytes C:\windows\system32\EBPPORT.DAT
030331220000 030331220000    68.2 KB C:\windows\system32\edit.com
030331220000 030331220000    10.5 KB C:\windows\system32\edit.hlp
030331220000 030331220000    12.3 KB C:\windows\system32\edlin.exe
050214161047 021114124310     120 KB C:\windows\system32\EEBAPI.dll
050214161047 021114124314     100 KB C:\windows\system32\EEBDSCVR.dll
050214161047 010821010000    53.0 KB C:\windows\system32\EEBSDKIF.dll
050214161047 020110200532    64.0 KB C:\windows\system32\EEBUtil.dll
030331220000 040804175642    26.0 KB C:\windows\system32\efsadu.dll
030331220000 030331220000     124 KB C:\windows\system32\ega.cpi
030331220000 040804175642     179 KB C:\windows\system32\els.dll
040726135559 040726135559    21.1 KB C:\windows\system32\emptyregdb.dat
<DIR> C:\windows\system32\en-US
040726182706 040804175642    20.0 KB C:\windows\system32\encapi.dll
030331220000 040804175642     182 KB C:\windows\system32\encdec.dll
040726233206 030331220000     101 KB C:\windows\system32\EqnClass.Dll
030331220000 040804175642    22.5 KB C:\windows\system32\ersvc.dll
040726163444 050726143945     237 KB C:\windows\system32\es.dll

	finder_proj.zip - A zip of the complete Visual Studio 2005 project. Version 1.3.0.0 published on 25-Aug-2007 corrects a bug where Dispose fails if zero results were found in the search.
	Win32FileFinder.cs.txt - The C# source file of the file finder classes (renamed to txt).
	FinderCommand.cs.txt - The C# source file for the console command driver class (renamed to txt).