//     Copyright (c) Microsoft Corporation.  All rights reserved.

using System;

using System.Collections;

using System.Collections.Generic;

using System.IO;

using System.Runtime.InteropServices;

using Microsoft.Experimental.IO.Interop;



namespace Microsoft.Experimental.IO {



    /// <summary>

    ///     Provides methods for creating, deleting, moving and enumerating directories and 

    ///     subdirectories with long paths, that is, paths that exceed 259 characters.

    /// </summary>

    public static class LongPathDirectory {



        /// <summary>

        ///     Creates the specified directory.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to create.

        /// </param>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        /// <remarks>

        ///     Note: Unlike <see cref="Directory.CreateDirectory(System.String)"/>, this method only creates 

        ///     the last directory in <paramref name="path"/>.

        /// </remarks>

        public static void Create(string path) {



            string normalizedPath = LongPathCommon.NormalizeLongPath(path);



            if (!NativeMethods.CreateDirectory(normalizedPath, IntPtr.Zero)) {



                // To mimic Directory.CreateDirectory, we don't throw if the directory (not a file) already exists

                int errorCode = Marshal.GetLastWin32Error();

                if (errorCode != NativeMethods.ERROR_ALREADY_EXISTS || !LongPathDirectory.Exists(path)) {

                    throw LongPathCommon.GetExceptionFromWin32Error(errorCode);

                }

            }

        }



        /// <summary>

        ///     Deletes the specified empty directory.

        /// </summary>

        /// <param name="path">

        ///      A <see cref="String"/> containing the path of the directory to delete.

        /// </param>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> could not be found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> refers to a directory that is read-only.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> refers to a directory that is not empty.

        ///     <para>

        ///         -or-    

        ///     </para>

        ///     <paramref name="path"/> refers to a directory that is in use.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static void Delete(string path) {



            string normalizedPath = LongPathCommon.NormalizeLongPath(path);



            if (!NativeMethods.RemoveDirectory(normalizedPath)) {

                throw LongPathCommon.GetExceptionFromLastWin32Error();

            }

        }



        /// <summary>

        ///     Returns a value indicating whether the specified path refers to an existing directory.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path to check.

        /// </param>

        /// <returns>

        ///     <see langword="true"/> if <paramref name="path"/> refers to an existing directory; 

        ///     otherwise, <see langword="false"/>.

        /// </returns>

        /// <remarks>

        ///     Note that this method will return false if any error occurs while trying to determine 

        ///     if the specified directory exists. This includes situations that would normally result in 

        ///     thrown exceptions including (but not limited to); passing in a directory name with invalid 

        ///     or too many characters, an I/O error such as a failing or missing disk, or if the caller

        ///     does not have Windows or Code Access Security (CAS) permissions to to read the directory.

        /// </remarks>

        public static bool Exists(string path) {



            bool isDirectory;

            if (LongPathCommon.Exists(path, out isDirectory)) {



                return isDirectory;

            }

            

            return false;

        }



        /// <summary>

        ///     Returns a enumerable containing the directory names of the specified directory.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to search.

        /// </param>

        /// <returns>

        ///     A <see cref="IEnumerable{T}"/> containing the directory names within <paramref name="path"/>.

        /// </returns>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static IEnumerable<string> EnumerateDirectories(string path) {



            return EnumerateDirectories(path, (string)null, SearchOption.TopDirectoryOnly);

        }



        /// <summary>

        ///     Returns a enumerable containing the directory names of the specified directory.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to search.

        /// </param>

        /// <param name="searchOption">

        ///     One of the <see cref="SearchOption"/> values that specifies whether the search operation should 

        ///     include all subdirectories or only the current directory.

        /// </param>

        /// <returns>

        ///     A <see cref="IEnumerable{T}"/> containing the directory names within <paramref name="path"/>.

        /// </returns>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static IEnumerable<string> EnumerateDirectories(string path, SearchOption searchOption)

        {



            return EnumerateDirectories(path, (string)null, searchOption);

        }



        /// <summary>

        ///     Returns a enumerable containing the directory names of the specified directory that 

        ///     match the specified search pattern.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to search.

        /// </param>

        /// <param name="searchPattern">

        ///     A <see cref="String"/> containing search pattern to match against the names of the 

        ///     directories in <paramref name="path"/>, otherwise, <see langword="null"/> or an empty 

        ///     string ("") to use the default search pattern, "*".

        /// </param>

        /// <returns>

        ///     A <see cref="IEnumerable{T}"/> containing the directory names within <paramref name="path"/>

        ///     that match <paramref name="searchPattern"/>.

        /// </returns>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static IEnumerable<string> EnumerateDirectories(string path, string searchPattern) {



            return EnumerateFileSystemEntries(path, searchPattern, true, false, SearchOption.TopDirectoryOnly);

        }



        /// <summary>

        ///     Returns a enumerable containing the directory names of the specified directory that 

        ///     match the specified search pattern.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to search.

        /// </param>

        /// <param name="searchPattern">

        ///     A <see cref="String"/> containing search pattern to match against the names of the 

        ///     directories in <paramref name="path"/>, otherwise, <see langword="null"/> or an empty 

        ///     string ("") to use the default search pattern, "*".

        /// </param>

        /// <param name="searchOption">

        ///     One of the <see cref="SearchOption"/> values that specifies whether the search operation should 

        ///     include all subdirectories or only the current directory.

        /// </param>

        /// <returns>

        ///     A <see cref="IEnumerable{T}"/> containing the directory names within <paramref name="path"/>

        ///     that match <paramref name="searchPattern"/>.

        /// </returns>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static IEnumerable<string> EnumerateDirectories(string path, string searchPattern, SearchOption searchOption)

        {



            return EnumerateFileSystemEntries(path, searchPattern, true, false, searchOption);

        }



        /// <summary>

        ///     Returns a enumerable containing the file names of the specified directory.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to search.

        /// </param>

        /// <returns>

        ///     A <see cref="IEnumerable{T}"/> containing the file names within <paramref name="path"/>.

        /// </returns>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static IEnumerable<string> EnumerateFiles(string path) {



            return EnumerateFiles(path, (string)null, SearchOption.TopDirectoryOnly);

        }



        /// <summary>

        ///     Returns a enumerable containing the file names of the specified directory.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to search.

        /// </param>

        /// <param name="searchOption">

        ///     One of the <see cref="SearchOption"/> values that specifies whether the search operation should 

        ///     include all subdirectories or only the current directory.

        /// </param>

        /// <returns>

        ///     A <see cref="IEnumerable{T}"/> containing the file names within <paramref name="path"/>.

        /// </returns>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static IEnumerable<string> EnumerateFiles(string path, SearchOption searchOption)

        {



            return EnumerateFiles(path, (string)null, searchOption);

        }



        /// <summary>

        ///     Returns a enumerable containing the file names of the specified directory that 

        ///     match the specified search pattern.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to search.

        /// </param>

        /// <param name="searchPattern">

        ///     A <see cref="String"/> containing search pattern to match against the names of the 

        ///     files in <paramref name="path"/>, otherwise, <see langword="null"/> or an empty 

        ///     string ("") to use the default search pattern, "*".

        /// </param>

        /// <returns>

        ///     A <see cref="IEnumerable{T}"/> containing the file names within <paramref name="path"/>

        ///     that match <paramref name="searchPattern"/>.

        /// </returns>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static IEnumerable<string> EnumerateFiles(string path, string searchPattern) {



            return EnumerateFileSystemEntries(path, searchPattern, false, true, SearchOption.TopDirectoryOnly);

        }



        /// <summary>

        ///     Returns a enumerable containing the file names of the specified directory that 

        ///     match the specified search pattern.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to search.

        /// </param>

        /// <param name="searchPattern">

        ///     A <see cref="String"/> containing search pattern to match against the names of the 

        ///     files in <paramref name="path"/>, otherwise, <see langword="null"/> or an empty 

        ///     string ("") to use the default search pattern, "*".

        /// </param>

        /// <param name="searchOption">

        ///     One of the <see cref="SearchOption"/> values that specifies whether the search operation should 

        ///     include all subdirectories or only the current directory.

        /// </param>

        /// <returns>

        ///     A <see cref="IEnumerable{T}"/> containing the file names within <paramref name="path"/>

        ///     that match <paramref name="searchPattern"/>.

        /// </returns>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static IEnumerable<string> EnumerateFiles(string path, string searchPattern, SearchOption searchOption)

        {

            return EnumerateFileSystemEntries(path, searchPattern, false, true, searchOption);

        }



        /// <summary>

        ///     Returns a enumerable containing the file and directory names of the specified directory.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to search.

        /// </param>

        /// <returns>

        ///     A <see cref="IEnumerable{T}"/> containing the file and directory names within 

        ///     <paramref name="path"/>.

        /// </returns>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static IEnumerable<string> EnumerateFileSystemEntries(string path) {



            return EnumerateFileSystemEntries(path, (string)null, SearchOption.TopDirectoryOnly);

        }



        /// <summary>

        ///     Returns a enumerable containing the file and directory names of the specified directory.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to search.

        /// </param>

        /// <param name="searchOption">

        ///     One of the <see cref="SearchOption"/> values that specifies whether the search operation should 

        ///     include all subdirectories or only the current directory.

        /// </param>

        /// <returns>

        ///     A <see cref="IEnumerable{T}"/> containing the file and directory names within 

        ///     <paramref name="path"/>.

        /// </returns>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static IEnumerable<string> EnumerateFileSystemEntries(string path, SearchOption searchOption)

        {



            return EnumerateFileSystemEntries(path, (string)null, searchOption);

        }



        /// <summary>

        ///     Returns a enumerable containing the file and directory names of the specified directory 

        ///     that match the specified search pattern.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to search.

        /// </param>

        /// <param name="searchPattern">

        ///     A <see cref="String"/> containing search pattern to match against the names of the 

        ///     files and directories in <paramref name="path"/>, otherwise, <see langword="null"/> 

        ///     or an empty string ("") to use the default search pattern, "*".

        /// </param>

        /// <returns>

        ///     A <see cref="IEnumerable{T}"/> containing the file and directory names within 

        ///     <paramref name="path"/>that match <paramref name="searchPattern"/>.

        /// </returns>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static IEnumerable<string> EnumerateFileSystemEntries(string path, string searchPattern) {

            

            return EnumerateFileSystemEntries(path, searchPattern, true, true, SearchOption.TopDirectoryOnly);

        }



        /// <summary>

        ///     Returns a enumerable containing the file and directory names of the specified directory 

        ///     that match the specified search pattern.

        /// </summary>

        /// <param name="path">

        ///     A <see cref="String"/> containing the path of the directory to search.

        /// </param>

        /// <param name="searchPattern">

        ///     A <see cref="String"/> containing search pattern to match against the names of the 

        ///     files and directories in <paramref name="path"/>, otherwise, <see langword="null"/> 

        ///     or an empty string ("") to use the default search pattern, "*".

        /// </param>

        /// <param name="searchOption">

        ///     One of the <see cref="SearchOption"/> values that specifies whether the search operation should 

        ///     include all subdirectories or only the current directory.

        /// </param>

        /// <returns>

        ///     A <see cref="IEnumerable{T}"/> containing the file and directory names within 

        ///     <paramref name="path"/>that match <paramref name="searchPattern"/>.

        /// </returns>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="path"/> is <see langword="null"/>.

        /// </exception>

        /// <exception cref="ArgumentException">

        ///     <paramref name="path"/> is an empty string (""), contains only white 

        ///     space, or contains one or more invalid characters as defined in 

        ///     <see cref="Path.GetInvalidPathChars()"/>.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> contains one or more components that exceed

        ///     the drive-defined maximum length. For example, on Windows-based 

        ///     platforms, components must not exceed 255 characters.

        /// </exception>

        /// <exception cref="PathTooLongException">

        ///     <paramref name="path"/> exceeds the system-defined maximum length. 

        ///     For example, on Windows-based platforms, paths must not exceed 

        ///     32,000 characters.

        /// </exception>

        /// <exception cref="DirectoryNotFoundException">

        ///     <paramref name="path"/> contains one or more directories that could not be

        ///     found.

        /// </exception>

        /// <exception cref="UnauthorizedAccessException">

        ///     The caller does not have the required access permissions.

        /// </exception>

        /// <exception cref="IOException">

        ///     <paramref name="path"/> is a file.

        ///     <para>

        ///         -or-

        ///     </para>

        ///     <paramref name="path"/> specifies a device that is not ready.

        /// </exception>

        public static IEnumerable<string> EnumerateFileSystemEntries(string path, string searchPattern, SearchOption searchOption)

        {

            return EnumerateFileSystemEntries(path, searchPattern, true, true, searchOption);

        }



        private static IEnumerable<string> EnumerateFileSystemEntries(string path, string searchPattern, bool includeDirectories, bool includeFiles, SearchOption searchOption) {



            string normalizedSearchPattern = LongPathCommon.NormalizeSearchPattern(searchPattern);

            string normalizedPath = LongPathCommon.NormalizeLongPath(path);



            // First check whether the specified path refers to a directory and exists

            FileAttributes attributes;

            int errorCode = LongPathCommon.TryGetDirectoryAttributes(normalizedPath, out attributes);

            if (errorCode != 0) {

                throw LongPathCommon.GetExceptionFromWin32Error(errorCode);

            }



            return EnumerateFileSystemIterator(normalizedPath, normalizedSearchPattern, includeDirectories, includeFiles, searchOption);

        }



        private static IEnumerable<string> EnumerateFileSystemIterator(string normalizedPath, string normalizedSearchPattern, bool includeDirectories, bool includeFiles, SearchOption searchOption) {

            // NOTE: Any exceptions thrown from this method are thrown on a call to IEnumerator<string>.MoveNext()

            Queue<string> directoryQueue = new Queue<string>();



            directoryQueue.Enqueue(normalizedPath);



            while(directoryQueue.Count > 0)

            {

                NativeMethods.WIN32_FIND_DATA findData;



                normalizedPath = directoryQueue.Dequeue();



                // Add subdirectories to search for files

                if (searchOption != SearchOption.TopDirectoryOnly)

                {

                    using (SafeFindHandle handle = BeginFind(Path.Combine(normalizedPath, "*"), out findData))

                    {

                        int errorCode;

                        if (handle == null)

                        {

                            errorCode = Marshal.GetLastWin32Error();

                            if (errorCode != NativeMethods.ERROR_FILE_NOT_FOUND && errorCode != 0)

                            {

                                throw LongPathCommon.GetExceptionFromWin32Error(errorCode);

                            }

                        }



                        do

                        {

                            string currentFileName = findData.cFileName;

                            if (IsDirectory(findData.dwFileAttributes))

                            {

                                if (!IsCurrentOrParentDirectory(currentFileName))

                                {

                                    directoryQueue.Enqueue(Path.Combine(normalizedPath, currentFileName));

                                }

                            }

                        }

                        while (NativeMethods.FindNextFile(handle, out findData));



                        errorCode = Marshal.GetLastWin32Error();

                        if (errorCode != NativeMethods.ERROR_NO_MORE_FILES)

                            throw LongPathCommon.GetExceptionFromWin32Error(errorCode);

                    }

                }



                string path = LongPathCommon.RemoveLongPathPrefix(normalizedPath);



                using (SafeFindHandle handle = BeginFind(Path.Combine(normalizedPath, normalizedSearchPattern), out findData))

                {

                    int errorCode;



                    if (handle == null)

                    {

                        errorCode = Marshal.GetLastWin32Error();

                        if (errorCode != NativeMethods.ERROR_FILE_NOT_FOUND && errorCode != 0)

                        {

                            throw LongPathCommon.GetExceptionFromWin32Error(errorCode);

                        }



                        continue;

                    }



                    do {

                        string currentFileName = findData.cFileName;



                        if (IsDirectory(findData.dwFileAttributes)) {

                            if (!IsCurrentOrParentDirectory(currentFileName)) {

                                if (includeDirectories) {

                                    yield return Path.Combine(path, currentFileName);

                                }

                            }

                        }

                        else {

                            if (includeFiles) {

                                yield return Path.Combine(path, currentFileName);

                            }

                        }

                    } while (NativeMethods.FindNextFile(handle, out findData));



                    errorCode = Marshal.GetLastWin32Error();

                    if (errorCode != NativeMethods.ERROR_NO_MORE_FILES)

                    {

                        throw LongPathCommon.GetExceptionFromWin32Error(errorCode);

                    }

                }

            }

        }



        private static SafeFindHandle BeginFind(string normalizedPathWithSearchPattern, out NativeMethods.WIN32_FIND_DATA findData) {

            

            SafeFindHandle handle = NativeMethods.FindFirstFile(normalizedPathWithSearchPattern, out findData);

            if (handle.IsInvalid) {



                int errorCode = Marshal.GetLastWin32Error();

                if (errorCode != NativeMethods.ERROR_FILE_NOT_FOUND)

                    throw LongPathCommon.GetExceptionFromWin32Error(errorCode);



                return null;

            }



            return handle;  

        }



        internal static bool IsDirectory(FileAttributes attributes) {



            return (attributes & FileAttributes.Directory) == FileAttributes.Directory;

        }



        private static bool IsCurrentOrParentDirectory(string directoryName) {



            return directoryName.Equals(".", StringComparison.OrdinalIgnoreCase) || directoryName.Equals("..", StringComparison.OrdinalIgnoreCase);

        }

    }

}