C# serialize and deserialize json to txt file

I would do it like follows:

public class Customer{    public string Id { get; set; }    public string Name { get; set; }    public string Address { get; set; }    public string Gender { get; set; }    public int Age { get; set; }}public void AddCustomer(Customer newCustomer){    var json = File.ReadAllText(pathToTheFile);    var customers = JsonConvert.DeserializeObject<List<Customer>>(json);    customers.Add(newCustomer);    File.WriteAllText(pathToTheFile, JsonConvert.SerializeObject(customers));}public Customer GetCustomer(string id){    var json = File.ReadAllText(pathToTheFile);    var customers = JsonConvert.DeserializeObject<List<Customer>>(json);    var result = new Customer();    foreach (var c in customers)    {        if (c.Id == id)        {            result = c;            break;        }    }    return result;}

Your problem is that you try to get a List of Customer from your file while you are saving only one customer.

If you want store multiple customers in your file you have to create a JArray and add your customer into it :

//The customers arrayprivate JArray customers = new JArray();//Store new customer in arraypublic int Store(string[] reservation){    JObject customer = new JObject(        new JProperty("id", this.getNewId()),        new JProperty("name", reservation[0]),        new JProperty("address", reservation[1]),        new JProperty("gender", reservation[2]),        new JProperty("age", reservation[3])    );    //Add customer to customers array    customers.add(customer);    return 1;}

Then, just save the JArray of customer :

//Save arraypublic void Save(){    StreamWriter file = File.CreateText(Settings.databasePath +  "customer.json");    using (JsonTextWriter writer = new JsonTextWriter(file))    {        //Save JArray of customers        customers.WriteTo(writer);    }}

You'll probably have to adapt this code to your own needs.

I try my best to write correct english, but be free to correct me.