Is there a way to ignore get-only properties in Json.NET without using JsonIgnore attributes?

c#, json, json.net

Solution

You can do this by implementing a custom `IContractResolver` and using that during serialization. If you subclass the `DefaultContractResolver`, this becomes very easy to do:

class WritablePropertiesOnlyResolver : DefaultContractResolver
{
    protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
    {
        IList<JsonProperty> props = base.CreateProperties(type, memberSerialization);
        return props.Where(p => p.Writable).ToList();
    }
}

Here is a test program demonstrating how to use it:

using System;
using System.Collections.Generic;
using System.Linq;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;

class Program
{
    static void Main(string[] args)
    {
        Widget w = new Widget { Id = 2, Name = "Joe Schmoe" };

        JsonSerializerSettings settings = new JsonSerializerSettings
        {
            ContractResolver = new WritablePropertiesOnlyResolver()
        };

        string json = JsonConvert.SerializeObject(w, settings);

        Console.WriteLine(json);
    }
}

class Widget
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string LowerCaseName
    {
        get { return (Name != null ? Name.ToLower() : null); }
    }
}

Here is the output of the above. Notice that the read-only property `LowerCaseName` is not included in the output.

{"Id":2,"Name":"Joe Schmoe"}

Problem

Is there a way to ignore get-only properties using the Json.NET serializer but without using `JsonIgnore` attributes? For example, I have a class with these get properties: ``` public Keys Hotkey { get; set; } public Keys KeyCode { get { return Hotkey & Keys.KeyCode; } } public Keys ModifiersKeys { get { return Hotkey & Keys.Modifiers; } } public bool Control { get { return (Hotkey & Keys.Control) == Keys.Control; } } public bool Shift { get { return (Hotkey & Keys.Shift) == Keys.Shift; } } public bool Alt { get { return (Hotkey & Keys.Alt) == Keys.Alt; } } public Modifiers ModifiersEnum { get { Modifiers modifiers = Modifiers.None; if (Alt) modifiers |= Modifiers.Alt; if (Control) modifiers |= Modifiers.Control; if (Shift) modifiers |= Modifiers.Shift; return modifiers; } } public bool IsOnlyModifiers { get { return KeyCode == Keys.ControlKey || KeyCode == Keys.ShiftKey || KeyCode == Keys.Menu; } } public bool IsValidKey { get { return KeyCode != Keys.None && !IsOnlyModifiers; } } ``` Do I need to add `[JsonIgnore]` to all of them (I also have many other classes), or there is better way to ignore all get-only properties?

Original source