Edit JSON file values without overwriting it in c#

April 18, 2022

I have this code and i want to edit json value but when i use something like this code another values goes "null" and i don’t want overwrite it i need to edit json value.

class cfg
{
        static void Main(string[] args)
        {
            generate_def();
            editvalues();
        }

        public static string defaultvalue = "off";

        public class Data
        {
            public string value { get; set; }
            public string value2 { get; set; }
        }

        public static void generate_def()
        {
            List<Data> _data = new List<Data>();
            _data.Add(new Data()
            {
                value = defaultvalue,
                value2 = defaultvalue,
            });

            string json = JsonConvert.SerializeObject(_data.ToArray());
            System.IO.File.WriteAllText("sample.json", json);
        }

        public static void editvalues()
        {
            List<Data> _data = new List<Data>();
            _data.Add(new Data()
            {
                value = "off",
            });

            string json = JsonConvert.SerializeObject(_data.ToArray());
            System.IO.File.WriteAllText("sample.json", json);
        }
}

my json file goes from this

[{"value":"off","value2":"off"}]

to this

[{"value":"on","value2":null}]

and i want

[{"value":"on","value2":"off"}]

>Solution :

you have to parse json before changing

public static void editvalues()
{
    var json = File.ReadAllText("sample.json");
    Data[] data = JsonConvert.DeserializeObject<Data[]>(json);
    data[0].value = "on";
    json = JsonConvert.SerializeObject(data);
    File.WriteAllText("sample.json", json);
}

or this

public static void editvalues()
{
    var json = File.ReadAllText("sample.json");

    var jsonArray= JArray.Parse(json);
    jsonArray[0]["value"] = "on";

    WriteAllText("sample.json", jsonArray.ToString());
}