PCFormat Forum Archive

Posted: **07 Sep 2010, 14:48**

H Guys

I am trying to search for all empty folders on my pc.

I am getting this error: "Access to the path 'd:\System Volume Information' is denied."

here is the code

Code: Select all


  DirectoryInfo di = new DirectoryInfo(@"d:\")
           
  DirectoryInfo[] dir = di.GetDirectories("*.*", SearchOption.AllDirectories );
 
  foreach (DirectoryInfo d in dir)
                {
                    FileInfo[] f = d.GetFiles();
                    if (f.Length == 0)
                    {
                      listBox1.Items.Add(f.ToString());
                    }
                }

Can anyone please help me with this.

Posted: **07 Sep 2010, 15:13**

"System Volume Information" is a protected operating system folder, that's why you can't access it.

Having a look at your code, I spotted two things:

You need to be able to handle the cases where the operating system denies you access to the folder that you're trying to view.
You're also not moving down the entire subfolder tree; instead, you're only going one level down. This is a situation where use of recursion would be perfect.

My approach to your problem would look like this:

Code: Select all

        public static void SearchEmptyFolders(DirectoryInfo baseFolder)
        {
            try
            {
                FileInfo[] fileList = baseFolder.GetFiles();
                if (fileList.Length == 0)
                {
                    Console.WriteLine("Folder {0} is empty.", baseFolder.FullName);
                }

                DirectoryInfo[] subFolders = baseFolder.GetDirectories();
                foreach (DirectoryInfo subfolder in subFolders)
                {
                    SearchEmptyFolders(subfolder);
                }
            }
            catch (UnauthorizedAccessException)
            {
                Console.WriteLine("Folder {0} could not be accessed.", baseFolder.FullName);
            }
        }

Posted: **08 Sep 2010, 07:26**

thanks alot:), going to read up on recursion now.

Posted: **08 Sep 2010, 07:28**

Go and google "recursion". Without reading a single hit you'll know how it works. One of those special google search words

Posted: **08 Sep 2010, 07:39**

Yeah you might even find a recursive link somewhere in there

Also if you want to make the code a tad more robust rather than just breaking out of the loot and causing other problems you might want to try using the System.Security.AccessControl.DirectorySecurity Class... You can check the security on the folder and see if you have rights. If you don't simply don't add it to the list or output. I assume you would actually like to do something with the list of empty folders once the recursive function if finished returning them all other than just writing them to the console. If so just slapping a try catch of the whole thing will result in you not getting back a result from the recursive function which in my opinion is lame.

Posted: **08 Sep 2010, 07:47**

busy studding for 70-536 and haven't got to the security yet, but will check it out.

checked google and the first link is http://en.wikipedia.org/wiki/Recursion

Thanks

Posted: **08 Sep 2010, 08:26**

But slapping a try catch within the foreach will work very well.

Posted: **08 Sep 2010, 08:42**

Recursion is cool.. but you have to look out for your stack... You can easily cause a stack overflow. Now on 32 and 64bit OS's the chance of it happening is remote but it can still happen.

just a simple template for recursive functions in C#

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public object Recursive(object value)
{
    object result;
    result = (new Random()).Next(1, 100);
    foreach(object o in objects)
    {
        result += Recursive(o);
    }
    return result;
}

Quick and dirty way of getting past the obstacle. Then you can actually use the result rather than just have it printed to the console.

Code: Select all

    public static System.Collections.ArrayList SearchEmptyFolders(System.IO.DirectoryInfo baseFolder)
    {
        System.Collections.ArrayList result = new ArrayList();
        try
        {
            System.IO.FileInfo[] fileList = baseFolder.GetFiles();
            if (fileList.Length == 0)
            {
                result.Add(baseFolder.FullName);
            }

            System.IO.DirectoryInfo[] subFolders = baseFolder.GetDirectories();
            foreach (System.IO.DirectoryInfo subfolder in subFolders)
            {
                result.AddRange(SearchEmptyFolders(subfolder));
            }
        }
        catch (UnauthorizedAccessException) {}
        return result;
    }

Bladerunner wrote:But slapping a try catch within the foreach will work very well.

No it won't as the exception is on the current folder not on the children. You get it from

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System.IO.FileInfo[] fileList = baseFolder.GetFiles();

or

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System.IO.DirectoryInfo[] subFolders = baseFolder.GetDirectories();

but the exception is still for the current folder. As such it won't even get to the loop.

Posted: **08 Sep 2010, 09:07**

Having said all that - when I tested the code snippet I posted earlier, I found that if you're getting access denied to a particular folder, you're extremely likely to get access denied for all its subfolders as well; hence I considered not running the loop in this scenario acceptable. Obviously, in a totally different scenario, you may want/need to still run the loop.

geraldhum wrote:thanks alot:), going to read up on recursion now.

The key to understanding recursion is to begin by understanding recursion. The rest is easy.

Posted: **08 Sep 2010, 09:17**

Ron2K wrote:Having said all that - when I tested the code snippet I posted earlier, I found that if you're getting access denied to a particular folder, you're extremely likely to get access denied for all its subfolders as well; hence I considered not running the loop in this scenario acceptable. Obviously, in a totally different scenario, you may want/need to still run the loop.

In that totally different scenario you still won't be able to as access rights filter down. If you don't have the read access to check for files in the folder you won't be able to check for folders either. So that if you have one of those scenarios where you have to look for a folder you have no rights to enumerate but have rights in the "invisible" folder, you would need to have the exact path of the "invisible" folder first.

Code: Select all

Folder1 [RW]
   Folder1.1 [RW]
   Folder1.2 [RW]
Folder2 [--]
   Folder2.1 [--]
   Folder2.2 [--]
   Folder2.3 [RW]
      Folder2.3.1 [RW]
      Folder2.3.2 [RW]
Folder3 [RW]
   Folder3.1 [RW]

Say that if you have no access to Folder2 but you have access to Folder2.3 then you won't be able to use Folder2 in order to enumerate Folder2.1, Folder2.1 and Folder2.3. You can however specify the full path to Folder2.3 and enumerate Folder2.3.1 and Folder2.3.2

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