1 file library that wraps FindFirstFileEx and FindNextFile Win32 functions to quickly enumerate the filesystem. This is an alternative to System.IO.File.GetFile and GetDirectory, this is mainly a toy exercise in performance. If you are trying to avoid exceptions in Directory.GetFiles, Marc Gravel has a great solution here: http://stackoverflow.c…

NativeFSEnumeration.cs

using System;
using System.IO;
using System.Collections.Generic;
using System.Runtime.InteropServices;

namespace NativeHelpers
{
    public static class NativeHelpers
    {
        //
        // Constants
        //
        const int  MAX_PATH                     = 260;
        const uint FILE_ATTRIBUTE_COMPRESSED    = 0x800;
        const uint FILE_ATTRIBUTE_DIRECTORY     = 0x10;
        const uint FILE_ATTRIBUTE_REPARSE_POINT = 0x400;
        const uint ERROR_NO_MORE_FILES          = 18;
        const Int64 INVALID_HANDLE_VALUE        = -1;
        

        // dwAdditionalFlags:
        const int FIND_FIRST_EX_CASE_SENSITIVE = 1;
        const int FIND_FIRST_EX_LARGE_FETCH = 2;

        //
        // Win32 Data Types
        //
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
        struct WIN32_FIND_DATA
        {
            public UInt32 dwFileAttributes;
            public System.Runtime.InteropServices.ComTypes.FILETIME ftCreationTime;
            public System.Runtime.InteropServices.ComTypes.FILETIME ftLastAccessTime;
            public System.Runtime.InteropServices.ComTypes.FILETIME ftLastWriteTime;
            public UInt32 nFileSizeHigh;
            public UInt32 nFileSizeLow;
            public UInt32 dwReserved0;
            public UInt32 dwReserved1;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
            public string cFileName;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 14)]
            public string cAlternateFileName;
        }


        enum FINDEX_INFO_LEVELS
        {
            FindExInfoStandard = 0,
            FindExInfoBasic = 1
        }


        enum FINDEX_SEARCH_OPS
        {
            FindExSearchNameMatch = 0,
            FindExSearchLimitToDirectories = 1,
            FindExSearchLimitToDevices = 2
        }


        //
        // Native Function Calls
        //
        [DllImport("kernel32.dll")]
        static extern bool FindClose(IntPtr hFindFile);


        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
        static extern IntPtr FindFirstFileEx(
                string lpFileName,
                FINDEX_INFO_LEVELS fInfoLevelId,
                out WIN32_FIND_DATA lpFindFileData,
                FINDEX_SEARCH_OPS fSearchOp,
                IntPtr lpSearchFilter,
                int dwAdditionalFlags);


        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1060:MovePInvokesToNativeMethodsClass"), DllImport("kernel32.dll", CharSet = CharSet.Auto)]
        static extern bool FindNextFile(IntPtr hFindFile, out WIN32_FIND_DATA lpFindFileData);


        //
        // Managed Methods
        //
        public static string[] GetFiles(string Path, string Pattern="*.*", bool BasicInfoLevel=true) {
            FileAttributes attr = File.GetAttributes(Path);  // Also serves to check if path exists
            var _path = ((attr & FileAttributes.Directory) == FileAttributes.Directory) ? Path : (new FileInfo(Path)).Directory.FullName;
            _path = System.IO.Path.Combine(_path, Pattern);

            var files = new System.Collections.Generic.List<string>();

            WIN32_FIND_DATA FindData;
            FINDEX_INFO_LEVELS InfoLevel = (BasicInfoLevel) ? FINDEX_INFO_LEVELS.FindExInfoBasic : FINDEX_INFO_LEVELS.FindExInfoStandard;


            IntPtr findHandle = FindFirstFileEx(_path, 
                                                InfoLevel,
                                                out FindData,
                                                FINDEX_SEARCH_OPS.FindExSearchNameMatch,
                                                IntPtr.Zero,
                                                FIND_FIRST_EX_LARGE_FETCH);

            if (findHandle.ToInt64() != INVALID_HANDLE_VALUE) {
                do {
                    if ( ! ((FindData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) == FILE_ATTRIBUTE_DIRECTORY)) {
                        files.Add(System.IO.Path.Combine(Path, FindData.cFileName));
                    }                    
                } while (FindNextFile(findHandle, out FindData));
            }

            FindClose(findHandle);

            return files.ToArray();
        }


        public static string[] GetDirectories(string Path, string Pattern="*.*", bool BasicInfoLevel=true) {
            
            FileAttributes attr = File.GetAttributes(Path);  // Also serves to check if path exists
            var _path = ((attr & FileAttributes.Directory) == FileAttributes.Directory) ? Path : (new FileInfo(Path)).Directory.FullName;
            _path = System.IO.Path.Combine(_path, Pattern);

            var dirs = new System.Collections.Generic.List<string>();

            WIN32_FIND_DATA FindData;
            FINDEX_INFO_LEVELS InfoLevel = (BasicInfoLevel) ? FINDEX_INFO_LEVELS.FindExInfoBasic : FINDEX_INFO_LEVELS.FindExInfoStandard;


            IntPtr findHandle = FindFirstFileEx(_path, 
                                                InfoLevel,
                                                out FindData,
                                                FINDEX_SEARCH_OPS.FindExSearchNameMatch,
                                                IntPtr.Zero,
                                                FIND_FIRST_EX_LARGE_FETCH);

            if (findHandle.ToInt64() != INVALID_HANDLE_VALUE) {
                do {
                    if ((FindData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) == FILE_ATTRIBUTE_DIRECTORY) {
                        dirs.Add(System.IO.Path.Combine(Path,FindData.cFileName));
                    }                    
                } while (FindNextFile(findHandle, out FindData));
            }

            FindClose(findHandle);

            return dirs.ToArray();
        }    
        

        public static string[] GetFilesRecurse(string Path, string Pattern="*.*") {
            
            WIN32_FIND_DATA FindData;
            FINDEX_INFO_LEVELS InfoLevel = FINDEX_INFO_LEVELS.FindExInfoBasic;
            IntPtr findHandle = new IntPtr(INVALID_HANDLE_VALUE);

            var files = new List<string>();
            var directories = new Stack<string>();
            string _path;

            FileAttributes attr = File.GetAttributes(Path);  // Also serves to check if path exists
            _path = ((attr & FileAttributes.Directory) == FileAttributes.Directory) ? Path : (new FileInfo(Path)).Directory.FullName;

            directories.Push(System.IO.Path.GetFullPath(_path));

            // stack processing loop
            while (directories.Count > 0) {

                _path = System.IO.Path.Combine(directories.Pop(),Pattern);
                findHandle = FindFirstFileEx(_path,
                                             InfoLevel,
                                             out FindData,
                                             FINDEX_SEARCH_OPS.FindExSearchNameMatch,
                                             IntPtr.Zero,
                                             FIND_FIRST_EX_LARGE_FETCH);

                if (findHandle.ToInt64() != INVALID_HANDLE_VALUE) {
                    do { // interate through dir contents loop
                        if (FindData.cFileName != "." && FindData.cFileName != "..") {
                            if (((FindData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != FILE_ATTRIBUTE_DIRECTORY)) { // check if it's a file
                                files.Add(System.IO.Path.Combine(_path.Replace(Pattern, ""), FindData.cFileName));
                            }
                            else {

                                directories.Push(System.IO.Path.Combine(_path.Replace(Pattern,""), FindData.cFileName));
                            }
                        }
                    } while (FindNextFile(findHandle, out FindData));
                }

                FindClose(findHandle);
                findHandle = new IntPtr(INVALID_HANDLE_VALUE);

#if DEBUG
                Console.WriteLine("D:{0,8} F:{1,16}", directories.Count, files.Count);
#endif
            }
            
            return files.ToArray();
        }

    }

}