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

Question

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?

Answer 1

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"}