diff --git a/2021/11/AccessibleDirectory.cs b/2021/11/AccessibleDirectory.cs
index ae18269..76aa427 100644
--- a/2021/11/AccessibleDirectory.cs
+++ b/2021/11/AccessibleDirectory.cs
@@ -3,75 +3,101 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
 
 namespace RyzStudio.IO
 {
     public class AccessibleDirectory
     {
 
-        public static List<string> GetFiles(string path, string pattern, bool searchTopOnly)
+        public static List<string> GetFiles(string path, string pattern, bool searchTopOnly) => GetFilesAsync(path, pattern, searchTopOnly).Result;
+
+        public static Task<List<string>> GetFilesAsync(string path, string pattern, bool searchTopOnly)
         {
-            List<string> fileList = new List<string>();
-            List<string> directoryList = new List<string>();
+            CancellationToken cancellationToken = new CancellationToken();
 
-            if (string.IsNullOrWhiteSpace(pattern)) pattern = "*";
+            return GetFilesAsync(path, pattern, searchTopOnly, cancellationToken);
+        }
 
-            directoryList.Add(path);
-
-            while (true)
+        public static Task<List<string>> GetFilesAsync(string path, string pattern, bool searchTopOnly, CancellationToken cancellationToken)
+        {
+            return Task.Run<List<string>>(() =>
             {
-                if (directoryList.Count <= 0)
+                List<string> fileList = new List<string>();
+                List<string> directoryList = new List<string>();
+
+                if (string.IsNullOrWhiteSpace(pattern)) pattern = "*";
+
+                if (cancellationToken.IsCancellationRequested) return fileList;
+
+                directoryList.Add(path);
+
+                while (true)
                 {
-                    break;
-                }
-
-                string directory = directoryList.First();
-                directoryList.RemoveAt(0);
-
-                if (IsDirectoryAccessible(directory))
-                {
-                    IEnumerable<string> searchDirList = new List<string>();
-
-                    try
+                    if (directoryList.Count <= 0)
                     {
-                        searchDirList = Directory.EnumerateDirectories(directory, "*", SearchOption.TopDirectoryOnly);
-                    }
-                    catch (Exception)
-                    {
-                        continue;
+                        break;
                     }
 
-                    if (!searchTopOnly)
+                    if (cancellationToken.IsCancellationRequested) return fileList;
+
+                    string directory = directoryList.First();
+                    directoryList.RemoveAt(0);
+
+                    if (IsDirectoryAccessible(directory))
                     {
-                        foreach (string item in searchDirList)
+                        IEnumerable<string> searchDirList = new List<string>();
+
+                        if (cancellationToken.IsCancellationRequested) return fileList;
+
+                        try
                         {
-                            if (!IsDirectoryAccessible(item))
+                            searchDirList = Directory.EnumerateDirectories(directory, "*", SearchOption.TopDirectoryOnly);
+                        }
+                        catch (Exception)
+                        {
+                            continue;
+                        }
+
+                        if (!searchTopOnly)
+                        {
+                            foreach (string item in searchDirList)
+                            {
+                                if (!IsDirectoryAccessible(item))
+                                {
+                                    continue;
+                                }
+
+                                directoryList.Add(item);
+                            }
+                        }
+
+                        foreach (string item in Directory.EnumerateFiles(directory, "*", SearchOption.TopDirectoryOnly))
+                        {
+                            if (cancellationToken.IsCancellationRequested) return fileList;
+
+                            if (!MatchFileSearchPattern(pattern, Path.GetFileName(item)))
                             {
                                 continue;
                             }
 
-                            directoryList.Add(item);
-                        }
-                    }
+                            if (!IsFileAccessible(item))
+                            {
+                                continue;
+                            }
 
-                    foreach (string item in Directory.EnumerateFiles(directory, "*", SearchOption.TopDirectoryOnly))
-                    {
-                        if (!MatchFileSearchPattern(pattern, Path.GetFileName(item)))
-                        {
-                            continue;
+                            fileList.Add(item);
+
+                            if (cancellationToken.IsCancellationRequested) return fileList;
                         }
 
-                        if (!IsFileAccessible(item))
-                        {
-                            continue;
-                        }
-
-                        fileList.Add(item);
+                        if (cancellationToken.IsCancellationRequested) return fileList;
                     }
                 }
-            }
 
-            return fileList;
+                return fileList;
+            });
         }
 
         public static IEnumerable<string> EnumerateFiles(string path, string pattern, bool searchTopOnly)
@@ -136,145 +162,179 @@ namespace RyzStudio.IO
             }
         }
 
-        public static void GetFiles(string path, string pattern, bool searchTopOnly, Func<string, ulong, int, bool> callback)
+        public static void GetFiles(string path, string pattern, bool searchTopOnly, Func<string, ulong, int, bool> callback) => GetFilesAsync(path, pattern, searchTopOnly, callback);
+
+        public static Task GetFilesAsync(string path, string pattern, bool searchTopOnly, Func<string, ulong, int, bool> callback)
         {
-            List<string> directoryList = new List<string>();
-            ulong searchCount = 0;
+            CancellationToken cancellationToken = new CancellationToken();
 
-            if (string.IsNullOrWhiteSpace(pattern)) pattern = "*";
+            return GetFilesAsync(path, pattern, searchTopOnly, callback, cancellationToken);
+        }
 
-            directoryList.Add(path);
-            searchCount++;
-
-            while (true)
+        public static Task GetFilesAsync(string path, string pattern, bool searchTopOnly, Func<string, ulong, int, bool> callback, CancellationToken cancellationToken)
+        {
+            return Task.Run(() =>
             {
-                if (directoryList.Count <= 0)
+                List<string> directoryList = new List<string>();
+                ulong searchCount = 0;
+
+                if (string.IsNullOrWhiteSpace(pattern)) pattern = "*";
+
+                if (cancellationToken.IsCancellationRequested) return;
+
+                directoryList.Add(path);
+                searchCount++;
+
+                while (true)
                 {
-                    break;
-                }
-
-                string directory = directoryList.First();
-                directoryList.RemoveAt(0);
-
-                callback(null, searchCount, directoryList.Count);
-
-                if (IsDirectoryAccessible(directory))
-                {
-                    IEnumerable<string> searchDirList = new List<string>();
-
-                    try
+                    if (directoryList.Count <= 0)
                     {
-                        searchDirList = Directory.EnumerateDirectories(directory, "*", SearchOption.TopDirectoryOnly);
-                    }
-                    catch (Exception)
-                    {
-                        continue;
+                        break;
                     }
 
-                    if (!searchTopOnly)
+                    if (cancellationToken.IsCancellationRequested) return;
+
+                    string directory = directoryList.First();
+                    directoryList.RemoveAt(0);
+
+                    callback(null, searchCount, directoryList.Count);
+
+                    if (IsDirectoryAccessible(directory))
                     {
-                        foreach (string item in searchDirList)
+                        IEnumerable<string> searchDirList = new List<string>();
+
+                        try
                         {
-                            if (!IsDirectoryAccessible(item))
+                            searchDirList = Directory.EnumerateDirectories(directory, "*", SearchOption.TopDirectoryOnly);
+                        }
+                        catch (Exception)
+                        {
+                            continue;
+                        }
+
+                        if (cancellationToken.IsCancellationRequested) return;
+
+                        if (!searchTopOnly)
+                        {
+                            foreach (string item in searchDirList)
+                            {
+                                if (!IsDirectoryAccessible(item))
+                                {
+                                    continue;
+                                }
+
+                                directoryList.Add(item);
+                                searchCount++;
+
+                                callback(null, searchCount, directoryList.Count);
+                            }
+                        }
+
+                        foreach (string item in Directory.EnumerateFiles(directory, "*", SearchOption.TopDirectoryOnly))
+                        {
+                            if (cancellationToken.IsCancellationRequested) return;
+
+                            if (!MatchFileSearchPattern(pattern, Path.GetFileName(item)))
                             {
                                 continue;
                             }
 
-                            directoryList.Add(item);
-                            searchCount++;
+                            if (!IsFileAccessible(item))
+                            {
+                                continue;
+                            }
 
-                            callback(null, searchCount, directoryList.Count);
+                            callback(item, searchCount, directoryList.Count);
+
+                            if (cancellationToken.IsCancellationRequested) return;
                         }
-                    }
 
-                    foreach (string item in Directory.EnumerateFiles(directory, "*", SearchOption.TopDirectoryOnly))
+                        if (cancellationToken.IsCancellationRequested) return;
+                    }
+                }
+            });
+        }
+
+        public static string GetNextFile(string filepath, string pattern) => GetNextFileAsync(filepath, pattern).Result;
+
+        public static Task<string> GetNextFileAsync(string filepath, string pattern)
+        {
+            return Task.Run(() =>
+            {
+                if (string.IsNullOrWhiteSpace(filepath)) return null;
+
+                string path = Path.GetDirectoryName(filepath);
+                if (string.IsNullOrWhiteSpace(path)) return null;
+
+                string filename = Path.GetFileName(filepath);
+                if (string.IsNullOrWhiteSpace(filename)) return null;
+
+                bool returnNext = false;
+                foreach (string item in Directory.EnumerateFiles(path, "*", SearchOption.TopDirectoryOnly))
+                {
+                    if (!MatchFileSearchPattern(pattern, Path.GetFileName(item)))
                     {
-                        if (!MatchFileSearchPattern(pattern, Path.GetFileName(item)))
-                        {
-                            continue;
-                        }
+                        continue;
+                    }
 
-                        if (!IsFileAccessible(item))
-                        {
-                            continue;
-                        }
+                    if (!IsFileAccessible(item))
+                    {
+                        continue;
+                    }
 
-                        callback(item, searchCount, directoryList.Count);
+                    if (returnNext)
+                    {
+                        return item;
+                    }
+
+                    if (Path.GetFileName(item).Equals(filename))
+                    {
+                        returnNext = true;
                     }
                 }
-            }
+
+                return null;
+            });
         }
 
-        public static string GetNextFile(string filepath, string pattern)
+        public static string GetPreviousFile(string filepath, string pattern) => GetPreviousFileAsync(filepath, pattern).Result;
+
+        public static Task<string> GetPreviousFileAsync(string filepath, string pattern)
         {
-            if (string.IsNullOrWhiteSpace(filepath)) return null;
-
-            string path = Path.GetDirectoryName(filepath);
-            if (string.IsNullOrWhiteSpace(path)) return null;
-
-            string filename = Path.GetFileName(filepath);
-            if (string.IsNullOrWhiteSpace(filename)) return null;
-
-            bool returnNext = false;
-            foreach (string item in Directory.EnumerateFiles(path, "*", SearchOption.TopDirectoryOnly))
+            return Task.Run(() =>
             {
-                if (!MatchFileSearchPattern(pattern, Path.GetFileName(item)))
+                if (string.IsNullOrWhiteSpace(filepath)) return null;
+
+                string path = Path.GetDirectoryName(filepath);
+                if (string.IsNullOrWhiteSpace(path)) return null;
+
+                string filename = Path.GetFileName(filepath);
+                if (string.IsNullOrWhiteSpace(filename)) return null;
+
+                StringBuilder sb = new StringBuilder();
+                foreach (string item in Directory.EnumerateFiles(path, "*", SearchOption.TopDirectoryOnly))
                 {
-                    continue;
+                    if (!MatchFileSearchPattern(pattern, Path.GetFileName(item)))
+                    {
+                        continue;
+                    }
+
+                    if (!IsFileAccessible(item))
+                    {
+                        continue;
+                    }
+
+                    sb.Clear();
+                    sb.Append(item);
+
+                    if (Path.GetFileName(item).Equals(filename))
+                    {
+                        return (sb.Length <= 0) ? null : sb.ToString();
+                    }
                 }
 
-                if (!IsFileAccessible(item))
-                {
-                    continue;
-                }
-
-                if (returnNext)
-                {
-                    return item;
-                }
-
-                if (Path.GetFileName(item).Equals(filename))
-                {
-                    returnNext = true;
-                }
-            }
-
-            return null;
-        }
-
-        public static string GetPreviousFile(string filepath, string pattern)
-        {
-            if (string.IsNullOrWhiteSpace(filepath)) return null;
-
-            string path = Path.GetDirectoryName(filepath);
-            if (string.IsNullOrWhiteSpace(path)) return null;
-
-            string filename = Path.GetFileName(filepath);
-            if (string.IsNullOrWhiteSpace(filename)) return null;
-
-            StringBuilder sb = new StringBuilder();
-            foreach (string item in Directory.EnumerateFiles(path, "*", SearchOption.TopDirectoryOnly))
-            {
-                if (!MatchFileSearchPattern(pattern, Path.GetFileName(item)))
-                {
-                    continue;
-                }
-
-                if (!IsFileAccessible(item))
-                {
-                    continue;
-                }
-
-                sb.Clear();
-                sb.Append(item);
-
-                if (Path.GetFileName(item).Equals(filename))
-                {
-                    return (sb.Length <= 0) ? null : sb.ToString();
-                }
-            }
-
-            return null;
+                return null;
+            });
         }
 
         public static bool IsAccessible(string path)