Solution.cs

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int x) { val = x; }
 * }
 */
public class Codec {
    public string serialize(TreeNode root) {
        return rserialize(root, "");
    }

    public TreeNode deserialize(string data) {
        string[] dataArray = data.Split(",");
        LinkedList<string> dataList = new LinkedList<string>(dataArray.ToList());
        return rdeserialize(dataList);
    }

    public string rserialize(TreeNode root, string str) {
        if (root == null) {
            str += "None,";
        } else {
            str += root.val.ToString() + ",";
            str = rserialize(root.left, str);
            str = rserialize(root.right, str);
        }
        return str;
    }
  
    public TreeNode rdeserialize(LinkedList<string> dataList) {
        if (dataList.First.Value.Equals("None")) {
            dataList.RemoveFirst();
            return null;
        }
  
        TreeNode root = new TreeNode(int.Parse(dataList.First.Value));
        dataList.RemoveFirst();
        root.left = rdeserialize(dataList);
        root.right = rdeserialize(dataList);
    
        return root;
    }
}

// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.deserialize(codec.serialize(root));