.NET (Core and Framework)

DirectoryInfo.GetDirectories exception

22-Nov-06 3:59

Use reflection to iterate through all the types in the current assembly/assemblies which inherit from System.Windows.Forms.Form

Formula 1 - Short for "F1 Racing" - named after the standard "help" key in Windows, it's a sport where participants desperately search through software help files trying to find actual documentation. It's tedious and somewhat cruel, most matches ending in a draw as no participant is able to find anything helpful. - Shog⁹

Ed

CPP_Student21-Nov-06 14:44

21-Nov-06 14:44

I am doing one of the Suggested Practices for the MCTS 70-536 exam prep book. The chapter 2 practice asks you to create an app that will search a drive for a particular file. So, I am trying to write a routine to search the c: drive for a file, but am having a problem with this:

DirectoryInfo[] dirs = dirInfo.GetDirectories("*.*", SearchOption.AllDirectories);

On this instruction it churns for a bit and then throws a System.UnauthorizedAccessException, and the Message of the exception is "Access to the path 'c:\System Volume Information' is denied."

If I change it to:

DirectoryInfo[] dirs = dirInfo.GetDirectories();

and recursively call the routine to search each subdirectory instead, it may find the file before the exception occurs, depending on what filename I give it. So, I cannot see how one could search a hard drive for a file using .NET.

Can anyone please help with this??

TIA

Ed.Poore22-Nov-06 4:03

22-Nov-06 4:03

Windows is not allowing you access to "C:\System Volume Information". You'll need to find a way of searching through directories, ignoreing those which you don't have permission to access.

CPP_Student22-Nov-06 11:45

22-Nov-06 11:45

If I cannot even get a list of the directories, how can I iterate through them to check their accessibility? I am using a Windows XP ID that has admistration abilities. I have not even tried to play with security issues yet using IDs that have limited access.

Is there any other way to get a list of the directories in c:\ ?

Thanks.

Ed.Poore22-Nov-06 12:24

22-Nov-06 12:24

Nobody (normally anyway) should be able to access System Volume Information since it's integral to the NTFS file system (I seem to remember).

The following (can be recursive) code works:

ConsoleColor def = Console.ForegroundColor;

foreach (string directory in Directory.GetDirectories("C:\\"))
{
	Console.WriteLine(directory);
	try
	{
		foreach (string subdirectory in Directory.GetDirectories(directory))
		{
			Console.WriteLine("\t{0}", subdirectory);
		}
	}
	catch // This should probably be replaced with a test for permissions.
	{
		Console.ForegroundColor = ConsoleColor.Red;
		Console.WriteLine("\tCould not iterate directory");
		Console.ForegroundColor = def;
	}
}
Console.ReadKey();

CPP_Student22-Nov-06 12:45

22-Nov-06 12:45

The GetDirectories() function returns an array of DirectoryInfo's, not strings. Besides, your code won't work either, since you have the foreach statement outside of the try block. It is on the foreach that it gets the exception. I just decided to pull the code out of the foreach statement so I could better figure out where it was getting the exception. So, I have this:

static void FindFile(DirectoryInfo dirInfo, string fileName, out FileInfo fileFound)<br />
		{<br />
			try<br />
			{<br />
				DirectoryInfo[] dirs = dirInfo.GetDirectories("*.*", SearchOption.AllDirectories);<br />
				foreach (DirectoryInfo di in dirs)<br />
				{<br />
					if ((di.Attributes & FileAttributes.System) == 0)<br />
					{<br />
						FileInfo fileI = SearchDirectory(di, fileName);<br />
						if (fileI != null)<br />
						{<br />
							fileFound = fileI;<br />
							return;<br />
						}<br />
					}<br />
				}<br />
			}<br />
			catch (System.UnauthorizedAccessException ex)<br />
			{<br />
				Console.WriteLine("Security EXCEPTION: {0}", ex.Message);<br />
				fileFound = null;<br />
				return;<br />
			}<br />
<br />
			catch (Exception ex)<br />
			{<br />
				Console.WriteLine("EXCEPTION: {0}", ex.ToString());<br />
				fileFound = null;<br />
				return;<br />
			}<br />
			fileFound = null;<br />
		}

It bombs on the first instruction (GetDirectories). Thkx

Ed.Poore22-Nov-06 13:21

22-Nov-06 13:21

Some points to note:

1) Directory.GetDirectories() returns an array of strings. Argue with the documentation & the code if you want but that's what it returns.
2) The code works just fine, I can copy and paste the results if you want but you may not understand them Suspicious | :suss:

3) Of course the code fails on the first line, you're still trying to recurse the directories, why my snippet did was demonstrate (perhaps too simply) that you needed to handle the recursion yourself so that you could continue searching rather than stopping when the exception occurred.

So in summary what you'll have to do is write a recursive routine which searches through a directory (not including the sub-directories), if it finds a file return it, if it can't read a directory then skip over it. And continue all the way through the loop.

sshhessh

CPP_Student22-Nov-06 13:50