diff --git a/codes/csharp/chapter_array_and_linkedlist/list.cs b/codes/csharp/chapter_array_and_linkedlist/list.cs
index 9530f24a..f8874029 100644
--- a/codes/csharp/chapter_array_and_linkedlist/list.cs
+++ b/codes/csharp/chapter_array_and_linkedlist/list.cs
@@ -1,11 +1,10 @@
-using Newtonsoft.Json.Linq;
+/**
+ * File: list.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
 using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using System.Xml.Linq;
 
 namespace hello_algo.chapter_array_and_linkedlist
 {
diff --git a/codes/csharp/chapter_array_and_linkedlist/my_list.cs b/codes/csharp/chapter_array_and_linkedlist/my_list.cs
index 8ccf3595..7ea09cf0 100644
--- a/codes/csharp/chapter_array_and_linkedlist/my_list.cs
+++ b/codes/csharp/chapter_array_and_linkedlist/my_list.cs
@@ -1,10 +1,10 @@
-using Newtonsoft.Json.Linq;
+/**
+ * File: my_list.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
 using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 
 namespace hello_algo.chapter_array_and_linkedlist
 {
diff --git a/codes/csharp/chapter_computational_complexity/leetcode_two_sum.cs b/codes/csharp/chapter_computational_complexity/leetcode_two_sum.cs
index d9498c32..6d45f99b 100644
--- a/codes/csharp/chapter_computational_complexity/leetcode_two_sum.cs
+++ b/codes/csharp/chapter_computational_complexity/leetcode_two_sum.cs
@@ -1,9 +1,10 @@
-using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+/**
+ * File: leetcode_two_sum.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using NUnit.Framework;
 
 namespace hello_algo.chapter_computational_complexity
 {
diff --git a/codes/csharp/chapter_computational_complexity/space_complexity.cs b/codes/csharp/chapter_computational_complexity/space_complexity.cs
index 97a16cdb..6148bf1b 100644
--- a/codes/csharp/chapter_computational_complexity/space_complexity.cs
+++ b/codes/csharp/chapter_computational_complexity/space_complexity.cs
@@ -1,10 +1,11 @@
-using hello_algo.include;
+/**
+ * File: space_complexity.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using hello_algo.include;
 using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 
 namespace hello_algo.chapter_computational_complexity
 {
diff --git a/codes/csharp/chapter_computational_complexity/time_complexity.cs b/codes/csharp/chapter_computational_complexity/time_complexity.cs
index 71c1036e..2bbd0176 100644
--- a/codes/csharp/chapter_computational_complexity/time_complexity.cs
+++ b/codes/csharp/chapter_computational_complexity/time_complexity.cs
@@ -1,4 +1,10 @@
-using NUnit.Framework;
+/**
+ * File: time_complexity.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using NUnit.Framework;
 
 namespace hello_algo.chapter_computational_complexity
 {
diff --git a/codes/csharp/chapter_computational_complexity/worst_best_time_complexity.cs b/codes/csharp/chapter_computational_complexity/worst_best_time_complexity.cs
index ebbcbeb0..67d9b4ef 100644
--- a/codes/csharp/chapter_computational_complexity/worst_best_time_complexity.cs
+++ b/codes/csharp/chapter_computational_complexity/worst_best_time_complexity.cs
@@ -1,8 +1,8 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+/**
+ * File: worst_best_time_complexity.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
 
 namespace hello_algo.chapter_computational_complexity
 {
diff --git a/codes/csharp/chapter_hashing/array_hash_map.cs b/codes/csharp/chapter_hashing/array_hash_map.cs
index cc564e26..3320fa85 100644
--- a/codes/csharp/chapter_hashing/array_hash_map.cs
+++ b/codes/csharp/chapter_hashing/array_hash_map.cs
@@ -1,7 +1,10 @@
+/**
+ * File: array_hash_map.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
 
-using hello_algo.include;
 using NUnit.Framework;
-using System.Collections.Immutable;
 
 namespace hello_algo.chapter_hashing
 {
diff --git a/codes/csharp/chapter_hashing/hash_map.cs b/codes/csharp/chapter_hashing/hash_map.cs
index ff86c88a..6afcc82c 100644
--- a/codes/csharp/chapter_hashing/hash_map.cs
+++ b/codes/csharp/chapter_hashing/hash_map.cs
@@ -1,7 +1,12 @@
 
+/**
+ * File: hash_map.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
 using hello_algo.include;
 using NUnit.Framework;
-using System.Collections.Immutable;
 
 namespace hello_algo.chapter_hashing
 {
diff --git a/codes/csharp/chapter_searching/binary_search.cs b/codes/csharp/chapter_searching/binary_search.cs
index bfe688c4..1bf8a5b2 100644
--- a/codes/csharp/chapter_searching/binary_search.cs
+++ b/codes/csharp/chapter_searching/binary_search.cs
@@ -1,9 +1,10 @@
-using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+/**
+ * File: binary_search.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using NUnit.Framework;
 
 namespace hello_algo.chapter_searching
 {
diff --git a/codes/csharp/chapter_searching/hashing_search.cs b/codes/csharp/chapter_searching/hashing_search.cs
index 6cc5f348..e4c2f2f2 100644
--- a/codes/csharp/chapter_searching/hashing_search.cs
+++ b/codes/csharp/chapter_searching/hashing_search.cs
@@ -1,11 +1,11 @@
-using hello_algo.include;
+/**
+ * File: hashing_search.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using hello_algo.include;
 using NUnit.Framework;
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 
 namespace hello_algo.chapter_searching
 {
diff --git a/codes/csharp/chapter_searching/linear_search.cs b/codes/csharp/chapter_searching/linear_search.cs
index ab22d8d2..412eb37d 100644
--- a/codes/csharp/chapter_searching/linear_search.cs
+++ b/codes/csharp/chapter_searching/linear_search.cs
@@ -1,10 +1,11 @@
-using hello_algo.include;
+/**
+ * File: linear_search.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using hello_algo.include;
 using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 
 namespace hello_algo.chapter_searching
 {
diff --git a/codes/csharp/chapter_sorting/bubble_sort.cs b/codes/csharp/chapter_sorting/bubble_sort.cs
index 3991f3aa..9506f797 100644
--- a/codes/csharp/chapter_sorting/bubble_sort.cs
+++ b/codes/csharp/chapter_sorting/bubble_sort.cs
@@ -1,9 +1,10 @@
-using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+/**
+ * File: bubble_sort.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using NUnit.Framework;
 
 namespace hello_algo.chapter_sorting
 {
diff --git a/codes/csharp/chapter_sorting/insertion_sort.cs b/codes/csharp/chapter_sorting/insertion_sort.cs
index 2e03b4fb..b5f87acf 100644
--- a/codes/csharp/chapter_sorting/insertion_sort.cs
+++ b/codes/csharp/chapter_sorting/insertion_sort.cs
@@ -1,4 +1,10 @@
-using NUnit.Framework;
+/**
+ * File: insertion_sort.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using NUnit.Framework;
 
 namespace hello_algo.chapter_sorting
 {
diff --git a/codes/csharp/chapter_sorting/merge_sort.cs b/codes/csharp/chapter_sorting/merge_sort.cs
index 11b45829..d7f9ff98 100644
--- a/codes/csharp/chapter_sorting/merge_sort.cs
+++ b/codes/csharp/chapter_sorting/merge_sort.cs
@@ -1,9 +1,10 @@
-using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+/**
+ * File: merge_sort.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using NUnit.Framework;
 
 namespace hello_algo.chapter_sorting
 {
diff --git a/codes/csharp/chapter_sorting/quick_sort.cs b/codes/csharp/chapter_sorting/quick_sort.cs
index ed9c37e0..020d4f34 100644
--- a/codes/csharp/chapter_sorting/quick_sort.cs
+++ b/codes/csharp/chapter_sorting/quick_sort.cs
@@ -1,9 +1,10 @@
-using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+/**
+ * File: quick_sort.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using NUnit.Framework;
 
 namespace hello_algo.chapter_sorting
 {
diff --git a/codes/csharp/chapter_stack_and_queue/array_queue.cs b/codes/csharp/chapter_stack_and_queue/array_queue.cs
index dc6b1403..5ad6115e 100644
--- a/codes/csharp/chapter_stack_and_queue/array_queue.cs
+++ b/codes/csharp/chapter_stack_and_queue/array_queue.cs
@@ -1,5 +1,9 @@
-using System;
-using hello_algo.include;
+/**
+ * File: array_queue.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
 using NUnit.Framework;
 
 namespace hello_algo.chapter_stack_and_queue
diff --git a/codes/csharp/chapter_stack_and_queue/array_stack.cs b/codes/csharp/chapter_stack_and_queue/array_stack.cs
index 5ce2dae6..b7ea6df7 100644
--- a/codes/csharp/chapter_stack_and_queue/array_stack.cs
+++ b/codes/csharp/chapter_stack_and_queue/array_stack.cs
@@ -1,5 +1,9 @@
-using System;
-using hello_algo.include;
+/**
+ * File: array_stack.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
 using NUnit.Framework;
 
 namespace hello_algo.chapter_stack_and_queue
diff --git a/codes/csharp/chapter_stack_and_queue/linkedlist_queue.cs b/codes/csharp/chapter_stack_and_queue/linkedlist_queue.cs
index 8d7c2796..70816c8f 100644
--- a/codes/csharp/chapter_stack_and_queue/linkedlist_queue.cs
+++ b/codes/csharp/chapter_stack_and_queue/linkedlist_queue.cs
@@ -1,4 +1,9 @@
-using System;
+/**
+ * File: linkedlist_queue.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
 using hello_algo.include;
 using NUnit.Framework;
 
diff --git a/codes/csharp/chapter_stack_and_queue/linkedlist_stack.cs b/codes/csharp/chapter_stack_and_queue/linkedlist_stack.cs
index 5ed82f2e..78a40944 100644
--- a/codes/csharp/chapter_stack_and_queue/linkedlist_stack.cs
+++ b/codes/csharp/chapter_stack_and_queue/linkedlist_stack.cs
@@ -1,4 +1,9 @@
-using System;
+/**
+ * File: linkedlist_stack.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
 using hello_algo.include;
 using NUnit.Framework;
 
diff --git a/codes/csharp/chapter_stack_and_queue/queue.cs b/codes/csharp/chapter_stack_and_queue/queue.cs
index d1ddbce9..a5ce9695 100644
--- a/codes/csharp/chapter_stack_and_queue/queue.cs
+++ b/codes/csharp/chapter_stack_and_queue/queue.cs
@@ -1,5 +1,9 @@
-using System;
-using hello_algo.include;
+/**
+ * File: queue.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
 using NUnit.Framework;
 
 namespace hello_algo.chapter_stack_and_queue
diff --git a/codes/csharp/chapter_stack_and_queue/stack.cs b/codes/csharp/chapter_stack_and_queue/stack.cs
index 7be10875..2595dea5 100644
--- a/codes/csharp/chapter_stack_and_queue/stack.cs
+++ b/codes/csharp/chapter_stack_and_queue/stack.cs
@@ -1,6 +1,10 @@
+/**
+ * File: stack.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
 
 using NUnit.Framework;
-using System.Collections.Immutable;
 
 namespace hello_algo.chapter_stack_and_queue
 {
@@ -18,7 +22,7 @@ namespace hello_algo.chapter_stack_and_queue
             stack.Push(2);
             stack.Push(5);
             stack.Push(4);
-            Console.WriteLine("栈 stack = " + String.Join(",", stack.ToImmutableArray()));
+            Console.WriteLine("栈 stack = " + string.Join(",", stack.ToArray()));
 
             /* 访问栈顶元素 */
             int peek = stack.Peek();
@@ -26,7 +30,7 @@ namespace hello_algo.chapter_stack_and_queue
 
             /* 元素出栈 */
             int pop = stack.Pop();
-            Console.WriteLine("出栈元素 pop = " + pop + "，出栈后 stack = " + String.Join(",", stack.ToImmutableArray()));
+            Console.WriteLine("出栈元素 pop = " + pop + "，出栈后 stack = " + string.Join(",", stack.ToArray()));
 
             /* 获取栈的长度 */
             int size = stack.Count();
diff --git a/codes/csharp/chapter_tree/avl_tree.cs b/codes/csharp/chapter_tree/avl_tree.cs
index 8d6a282b..7cef6231 100644
--- a/codes/csharp/chapter_tree/avl_tree.cs
+++ b/codes/csharp/chapter_tree/avl_tree.cs
@@ -1,6 +1,11 @@
-using hello_algo.include;
+/**
+ * File: avl_tree.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using hello_algo.include;
 using NUnit.Framework;
-using System.Collections.Generic;
 
 namespace hello_algo.chapter_tree
 {
@@ -69,7 +74,7 @@ namespace hello_algo.chapter_tree
         }
 
         /* 执行旋转操作，使该子树重新恢复平衡 */
-        private TreeNode? rotate(TreeNode? node)
+        TreeNode? rotate(TreeNode? node)
         {
             if (node == null)
                 return node;
diff --git a/codes/csharp/chapter_tree/binary_search_tree.cs b/codes/csharp/chapter_tree/binary_search_tree.cs
index 9d52d000..00958dcb 100644
--- a/codes/csharp/chapter_tree/binary_search_tree.cs
+++ b/codes/csharp/chapter_tree/binary_search_tree.cs
@@ -1,7 +1,11 @@
-using hello_algo.include;
-using NUnit.Framework;
-using System.Collections.Generic;
+/**
+ * File: binary_search_tree.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
 
+using hello_algo.include;
+using NUnit.Framework;
 
 namespace hello_algo.chapter_tree
 {
@@ -31,11 +35,7 @@ namespace hello_algo.chapter_tree
             return cur;
         }
 
-        /// <summary>
-        /// 插入结点
-        /// </summary>
-        /// <param name="num"></param>
-        /// <returns></returns>
+        /* 插入结点 */
         TreeNode? insert(int num)
         {
             // 若树为空，直接提前返回
diff --git a/codes/csharp/chapter_tree/binary_tree.cs b/codes/csharp/chapter_tree/binary_tree.cs
index d3893e79..88b5f767 100644
--- a/codes/csharp/chapter_tree/binary_tree.cs
+++ b/codes/csharp/chapter_tree/binary_tree.cs
@@ -1,7 +1,11 @@
+/**
+ * File: binary_tree.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
 using hello_algo.include;
 using NUnit.Framework;
-using System.Collections.Generic;
-
 
 namespace hello_algo.chapter_tree
 {
diff --git a/codes/csharp/chapter_tree/binary_tree_bfs.cs b/codes/csharp/chapter_tree/binary_tree_bfs.cs
index 2715783a..b686c889 100644
--- a/codes/csharp/chapter_tree/binary_tree_bfs.cs
+++ b/codes/csharp/chapter_tree/binary_tree_bfs.cs
@@ -1,4 +1,10 @@
-using hello_algo.include;
+/**
+ * File: binary_tree_bfs.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using hello_algo.include;
 using NUnit.Framework;
 
 namespace hello_algo.chapter_tree
diff --git a/codes/csharp/include/PrintUtil.cs b/codes/csharp/include/PrintUtil.cs
index bdd436ea..3249c3ea 100644
--- a/codes/csharp/include/PrintUtil.cs
+++ b/codes/csharp/include/PrintUtil.cs
@@ -1,9 +1,8 @@
-using System;
-using System.Collections.Generic;
-using System.Diagnostics.SymbolStore;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+/**
+ * File: PrintUtil.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
 
 namespace hello_algo.include
 {
diff --git a/codes/csharp/include/TreeNode.cs b/codes/csharp/include/TreeNode.cs
index d9130b22..69dd59b4 100644
--- a/codes/csharp/include/TreeNode.cs
+++ b/codes/csharp/include/TreeNode.cs
@@ -1,3 +1,9 @@
+/**
+ * File: TreeNode.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
 namespace hello_algo.include
 {
     public class TreeNode