diff --git a/cs/maximum-level-sum-of-a-binary-tree.cs b/cs/maximum-level-sum-of-a-binary-tree.cs
new file mode 100644
index 0000000..0e89e8b
--- /dev/null
+++ b/cs/maximum-level-sum-of-a-binary-tree.cs
@@ -0,0 +1,43 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private void MaxSum(List<int> levels, int level, TreeNode node) {
+        if (node == null) {
+            return;
+        }
+
+        while (level >= levels.Count) {
+            levels.Add(0);
+        }
+        levels[level] += node.val;
+
+        MaxSum(levels, level + 1, node.left);
+        MaxSum(levels, level + 1, node.right);
+    }
+
+    public int MaxLevelSum(TreeNode root) {
+        var levels = new List<int>();
+
+        MaxSum(levels, 0, root);
+
+        var maxIdx = 0;
+        for (var i = 1; i < levels.Count; ++i) {
+            if (levels[i] > levels[maxIdx]) {
+                maxIdx = i;
+            }
+        }
+
+        return maxIdx + 1;
+    }
+}