How to Get a List of Files and Folders Without Directory.GetFiles Access Denied Error

I know the title is a bit long, but it descriptive of the problem. Recently I had need to retrieve a listing of files and folders given a root path. All worked well, until I tested on Vista and Windows 7 machines. When trying to browse the "Users" folder, I kept getting access denied errors and no lists returned. The problem is that Directory.GetFiles and Directory.GetDirectories will fail on the first sign of an access denied issue. On Vista and Windows 7, most of the directories under the Users folder are ACL'd to not allow reading or browsing.

The solution is to use a DirectoryInfo object to get the list of directories, and loop through those. The solution I present below uses PLINQ (Parallel LINQ) for multi-threaded looping. If you do not have PLINQ installed, simply change the Parallel.ForEach statements to the standard ForEach.

Notice the use of a Predicate in both functions. This allows you to add advanced filtering, for example only returning files with an extension of ".jpg", or only returning files modified in the last five days.

using System; 
using System.IO; 
using System.Threading; 
  
namespace MStaller 
{ 
    internal static class DirectoryListing 
    { 
        #region DirectoryList 
  
        /// <summary> 
        /// Returns a list of directories under RootDirectory 
        /// </summary> 
        /// <param name="RootDirectory">starting directory</param> 
        /// <param name="SearchAllDirectories">when true, all sub directories
        ///             will be searched as well</param> 
        /// <param name="Filter">filter to be done on directory. use null for no
        ///                      filtering</param> 
        public static List<string> DirectoryList(string RootDirectory,
            bool SearchAllDirectories, Predicate<string> Filter) 
        { 
            List<string> retList = new List<string>(); 
  
            try 
            { 
                // create a directory info object 
                DirectoryInfo di = new DirectoryInfo(RootDirectory); 
  
                // loop through directories populating the list 
                Parallel.ForEach(di.GetDirectories(), folder => 
                { 
                    try 
                    { 
                        // add the folder if it passes the filter 
                        if ((Filter == null) || (Filter(folder.FullName))) 
                        { 
                            // add the folder 
                            retList.Add(folder.FullName); 
  
                            // get it's sub folders 
                            if (SearchAllDirectories) 
                                retList.AddRange(DirectoryList(folder.FullName, true,
                                    Filter)); 
                        } 
                    } 
 
                    catch (UnauthorizedAccessException) 
                    { 
                        // don't really need to do anything 
                        // user just doesn't have access 
                    } 
  
                    catch (Exception excep) 
                    { 
                        // TODO: log the exception 
                    } 
                }); 
            } 
  
            catch (Exception excep) 
            { 
                // TODO: save exception 
            } 
  
            // return the list 
            return retList; 
        } 
  
        // DirectoryList 
        #endregion 
  
        #region FileList 
  
        /// <summary> 
        /// Returns a list of files under RootDirectory 
        /// </summary> 
        /// <param name="RootDirectory">starting directory</param> 
        /// <param name="SearchAllDirectories">when true, all sub directories will
        ///              be searched as well</param> 
        /// <param name="Filter">filter to be done on files/directory. use null for no
        ///              filtering</param> 
        public static List<string> FileList(string RootDirectory,
            bool SearchAllDirectories, Predicate<string> Filter) 
        { 
            List<string> retList = new List<string>(); 
  
            try 
            { 
                // get the list of directories 
                List<string> DirList = new List<string> { RootDirectory }; 
  
                // get sub directories if allowed 
                if (SearchAllDirectories) 
                    DirList.AddRange(DirectoryList(RootDirectory, true, null)); 
  
                // loop through directories populating the list 
                Parallel.ForEach(DirList, folder => 
                { 
                    // get a directory object 
                    DirectoryInfo di = new DirectoryInfo(folder); 
  
                    try 
                    { 
                        // loop through the files in this directory 
                        foreach (FileInfo file in di.GetFiles()) 
                        { 
                            try 
                            { 
                                // add the file if it passes the filter 
                                if ((Filter == null) || (Filter(file.FullName))) 
                                    retList.Add(file.FullName); 
                            } 
  
                            catch (Exception excep) 
                            { 
                                // TODO: log the exception 
                            } 
                        } 
                    } 
  
                    catch (UnauthorizedAccessException) 
                    { 
                        // don't really need to do anything 
                        // user just doesn't have access 
                    } 
  
                    catch (Exception excep) 
                    { 
                        // TODO: log the exception 
                    } 
                }); 
            } 
  
            catch (Exception excep) 
            { 
                // TODO: save exception 
            } 
  
            // return the list 
            return retList; 
        } 
  
        // FileList 
        #endregion 
    } 
}