diff --git a/problems/0110.平衡二叉树.md b/problems/0110.平衡二叉树.md
index c7df9c8f..41669bff 100644
--- a/problems/0110.平衡二叉树.md
+++ b/problems/0110.平衡二叉树.md
@@ -908,6 +908,31 @@ impl Solution {
     }
 }
 ```
+### C#
+```C#
+public bool IsBalanced(TreeNode root)
+{
+    return GetHeight(root) == -1 ? false : true;
+}
+public int GetHeight(TreeNode root)
+{
+    if (root == null) return 0;
+    int left = GetHeight(root.left);
+    if (left == -1) return -1;
+    int right = GetHeight(root.right);
+    if (right == -1) return -1;
+    int res;
+    if (Math.Abs(left - right) > 1)
+    {
+        res = -1;
+    }
+    else
+    {
+        res = 1 + Math.Max(left, right);
+    }
+    return res;
+}
+```
 
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diff --git a/problems/0111.二叉树的最小深度.md b/problems/0111.二叉树的最小深度.md
index c4e55a07..b27df4a6 100644
--- a/problems/0111.二叉树的最小深度.md
+++ b/problems/0111.二叉树的最小深度.md
@@ -708,6 +708,49 @@ impl Solution {
     }
 }
 ```
+### C#
+```C#
+// 递归
+public int MinDepth(TreeNode root)
+{
+    if (root == null) return 0;
+    int left = MinDepth(root.left);
+    int right = MinDepth(root.right);
+    if (root.left == null && root.right != null)
+        return 1+right;
+    else if(root.left!=null && root.right == null)
+        return 1+left;
+        
+    int res = 1 + Math.Min(left, right);
+    return res;
+}
+```
+```C#
+// 迭代
+public int MinDepth(TreeNode root)
+{
+    if (root == null) return 0;
+    int depth = 0;
+    var que = new Queue<TreeNode>();
+    que.Enqueue(root);
+    while (que.Count > 0)
+    {
+        int size = que.Count;
+        depth++;
+        for (int i = 0; i < size; i++)
+        {
+            var node = que.Dequeue();
+            if (node.left != null)
+                que.Enqueue(node.left);
+            if (node.right != null)
+                que.Enqueue(node.right);
+            if (node.left == null && node.right == null)
+                return depth;
+        }
+    }
+    return depth;
+}     
+```
 
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diff --git a/problems/0222.完全二叉树的节点个数.md b/problems/0222.完全二叉树的节点个数.md
index d54f9b85..ef6e88aa 100644
--- a/problems/0222.完全二叉树的节点个数.md
+++ b/problems/0222.完全二叉树的节点个数.md
@@ -867,6 +867,31 @@ impl Solution {
     }
 }
 ```
+### C#
+```C#
+// 递归
+public int CountNodes(TreeNode root)
+{
+    if (root == null) return 0;
+    var left = root.left;
+    var right = root.right;
+    int leftDepth = 0, rightDepth = 0;
+    while (left != null)
+    {
+        left = left.left;
+        leftDepth++;
+    }
+    while (right != null)
+    {
+        right = right.right;
+        rightDepth++;
+    }
+    if (leftDepth == rightDepth)
+        return (int)Math.Pow(2, leftDepth+1) - 1;
+    return CountNodes(root.left) + CountNodes(root.right) + 1;
+
+}
+```
 
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