C＃treeview未经授权的异常

Question

So I followed MS article http://msdn.microsoft.com/en-us/library/ms171645.aspx

This is Creating an Explorer Style Interface with the ListView and TreeView Controls Using the Designer.

So all is well, howerver, is you set it to the root of C to scan all the folders and files etc. I receive {"Access to the path '<path to file' is denied."}

VS 2010 points this spot that is the issue.

subSubDirs = subDir.GetDirectories();

I can put a try catch around this are, howerver, after the exception is thrown the app doesn't continue.

Is there a way I can skip directories that the app cannot access?

Answer 1

You might have the try catch in the wrong place. Based on the code in the walkthrough you could put the try catch like this:

Replace:

subSubDirs = subDir.GetDirectories();

with this:

try 
{
    subSubDirs = subDir.GetDirectories();
}
catch(UnauthorizedAccessException uae)
{
  //log that subDir.GetDirectories was not possible
}

Also, the line:

if (subSubDirs.Length != 0)

should be changed to:

if (subSubDirs != null && subSubDirs.Length != 0)

Answer 2

You get the exception because the calling account doesn't have access rights to folders like System Volume Information . You can get around this some by using Linq and skipping folders that are marked System or Hidden .

DirectoryInfo root = new DirectoryInfo(@"C:\");

Func<FileSystemInfo, Boolean> predicate = dir =>
    (dir.Attributes & FileAttributes.System) != FileAttributes.System &&
    (dir.Attributes & FileAttributes.Hidden) != FileAttributes.Hidden;

IEnumerable<FileSystemInfo> directories = root.GetDirectories().Where(predicate);

foreach (DirectoryInfo directory in directories) {
    try {
        Trace.WriteLine(directory.Name);
        DirectoryInfo[] subdirectories = directory.GetDirectories();
    }
    catch (System.UnauthorizedAccessException) {
        Trace.WriteLine("Insufficient access rights.");
    }
}

Trace.WriteLine("End of application.");

This is not solution for every scenario though, and will fail on some files and folders. There is no easy solution using the existing API; you may want to look into getting file and directory information through WMI instead.