Demonstration that the code provided with the JSON provided works

Program.cs

using Newtonsoft.Json;

string json = "{\"Code\":\"AA10\",\"day\":\"monday\",\"errors\":[]}";

var newyvar = JsonConvert.DeserializeObject<Dictionary<string, object>>(json);
string new_row = Convert.ToString(newyvar["Code"]) + ";" + "New";

Console.WriteLine(new_row);