diff --git a/codes/csharp/chapter_backtracking/subset_sum_i.cs b/codes/csharp/chapter_backtracking/subset_sum_i.cs
new file mode 100644
index 000000000..1840e074a
--- /dev/null
+++ b/codes/csharp/chapter_backtracking/subset_sum_i.cs
@@ -0,0 +1,55 @@
+/**
+* File: subset_sum_i.cs
+* Created Time: 2023-06-25
+* Author: hpstory (hpstory1024@163.com)
+*/
+
+namespace hello_algo.chapter_backtracking; 
+
+public class subset_sum_i {
+    /* 回溯算法：子集和 I */
+    public static void backtrack(List<int> state, int target, int[] choices, int start, List<List<int>> res) {
+        // 子集和等于 target 时，记录解
+        if (target == 0) {
+            res.Add(new List<int>(state));
+            return;
+        }
+        // 遍历所有选择
+        // 剪枝二：从 start 开始遍历，避免生成重复子集
+        for (int i = start; i < choices.Length; i++) {
+            // 剪枝一：若子集和超过 target ，则直接结束循环
+            // 这是因为数组已排序，后边元素更大，子集和一定超过 target
+            if (target - choices[i] < 0) {
+                break;
+            }
+            // 尝试：做出选择，更新 target, start
+            state.Add(choices[i]);
+            // 进行下一轮选择
+            backtrack(state, target - choices[i], choices, i, res);
+            // 回退：撤销选择，恢复到之前的状态
+            state.RemoveAt(state.Count - 1);
+        }
+    }
+
+    /* 求解子集和 I */
+    public static List<List<int>> subsetSumI(int[] nums, int target) {
+        List<int> state = new List<int>(); // 状态（子集）
+        Array.Sort(nums); // 对 nums 进行排序
+        int start = 0; // 遍历起始点
+        List<List<int>> res = new List<List<int>>(); // 结果列表（子集列表）
+        backtrack(state, target, nums, start, res);
+        return res;
+    }
+
+    [Test]
+    public void Test() {
+        int[] nums = { 3, 4, 5 };
+        int target = 9;
+        List<List<int>> res = subsetSumI(nums, target);
+        Console.WriteLine("输入数组 nums = " + string.Join(", ", nums) + ", target = " + target);
+        Console.WriteLine("所有和等于 " + target + " 的子集 res = ");
+        foreach (var subset in res) {
+            PrintUtil.PrintList(subset);
+        }
+    }
+}
diff --git a/codes/csharp/chapter_backtracking/subset_sum_i_naive.cs b/codes/csharp/chapter_backtracking/subset_sum_i_naive.cs
new file mode 100644
index 000000000..6e16ed78c
--- /dev/null
+++ b/codes/csharp/chapter_backtracking/subset_sum_i_naive.cs
@@ -0,0 +1,53 @@
+/**
+* File: subset_sum_i_naive.cs
+* Created Time: 2023-06-25
+* Author: hpstory (hpstory1024@163.com)
+*/
+
+namespace hello_algo.chapter_backtracking; 
+
+public class subset_sum_i_naive {
+    /* 回溯算法：子集和 I */
+    public static void backtrack(List<int> state, int target, int total, int[] choices, List<List<int>> res) {
+        // 子集和等于 target 时，记录解
+        if (total == target) {
+            res.Add(new List<int>(state));
+            return;
+        }
+        // 遍历所有选择
+        for (int i = 0; i < choices.Length; i++) {
+            // 剪枝：若子集和超过 target ，则跳过该选择
+            if (total + choices[i] > target) {
+                continue;
+            }
+            // 尝试：做出选择，更新元素和 total
+            state.Add(choices[i]);
+            // 进行下一轮选择
+            backtrack(state, target, total + choices[i], choices, res);
+            // 回退：撤销选择，恢复到之前的状态
+            state.RemoveAt(state.Count - 1);
+        }
+    }
+
+    /* 求解子集和 I（包含重复子集） */
+    public static List<List<int>> subsetSumINaive(int[] nums, int target) {
+        List<int> state = new List<int>(); // 状态（子集）
+        int total = 0; // 子集和
+        List<List<int>> res = new List<List<int>>(); // 结果列表（子集列表）
+        backtrack(state, target, total, nums, res);
+        return res;
+    }
+
+    [Test]
+    public void Test() {
+        int[] nums = { 3, 4, 5 };
+        int target = 9;
+        List<List<int>> res = subsetSumINaive(nums, target);
+        Console.WriteLine("输入数组 nums = " + string.Join(", ", nums) + ", target = " + target);
+        Console.WriteLine("所有和等于 " + target + " 的子集 res = ");
+        foreach (var subset in res) {
+            PrintUtil.PrintList(subset);
+        }
+        Console.WriteLine("请注意，该方法输出的结果包含重复集合");
+    }
+}
diff --git a/codes/csharp/chapter_backtracking/subset_sum_ii.cs b/codes/csharp/chapter_backtracking/subset_sum_ii.cs
new file mode 100644
index 000000000..dec1ef317
--- /dev/null
+++ b/codes/csharp/chapter_backtracking/subset_sum_ii.cs
@@ -0,0 +1,60 @@
+/**
+* File: subset_sum_ii.cs
+* Created Time: 2023-06-25
+* Author: hpstory (hpstory1024@163.com)
+*/
+
+namespace hello_algo.chapter_backtracking; 
+
+public class subset_sum_ii {
+    /* 回溯算法：子集和 II */
+    public static void backtrack(List<int> state, int target, int[] choices, int start, List<List<int>> res) {
+        // 子集和等于 target 时，记录解
+        if (target == 0) {
+            res.Add(new List<int>(state));
+            return;
+        }
+        // 遍历所有选择
+        // 剪枝二：从 start 开始遍历，避免生成重复子集
+        // 剪枝三：从 start 开始遍历，避免重复选择同一元素
+        for (int i = start; i < choices.Length; i++) {
+            // 剪枝一：若子集和超过 target ，则直接结束循环
+            // 这是因为数组已排序，后边元素更大，子集和一定超过 target
+            if (target - choices[i] < 0) {
+                break;
+            }
+            // 剪枝四：如果该元素与左边元素相等，说明该搜索分支重复，直接跳过
+            if (i > start && choices[i] == choices[i - 1]) {
+                continue;
+            }
+            // 尝试：做出选择，更新 target, start
+            state.Add(choices[i]);
+            // 进行下一轮选择
+            backtrack(state, target - choices[i], choices, i + 1, res);
+            // 回退：撤销选择，恢复到之前的状态
+            state.RemoveAt(state.Count - 1);
+        }
+    }
+
+    /* 求解子集和 II */
+    public static List<List<int>> subsetSumII(int[] nums, int target) {
+        List<int> state = new List<int>(); // 状态（子集）
+        Array.Sort(nums); // 对 nums 进行排序
+        int start = 0; // 遍历起始点
+        List<List<int>> res = new List<List<int>>(); // 结果列表（子集列表）
+        backtrack(state, target, nums, start, res);
+        return res;
+    }
+
+    [Test]
+    public void Test() {
+        int[] nums = { 4, 4, 5 };
+        int target = 9;
+        List<List<int>> res = subsetSumII(nums, target);
+        Console.WriteLine("输入数组 nums = " + string.Join(", ", nums) + ", target = " + target);
+        Console.WriteLine("所有和等于 " + target + " 的子集 res = ");
+        foreach (var subset in res) {
+            PrintUtil.PrintList(subset);
+        }
+    }
+}