Serialization of F# mutable variable to JSON using Json.NET generates duplicated items

Question

Here is my code:

 open Newtonsoft.Json
 open Newtonsoft.Json.Converters

 type T = {
     mutable name : string;
     mutable height : int;
     }

 let a = { name = "abc"; height = 180;}
 a.height  <- 200
 let b = JsonConvert.SerializeObject(a, Formatting.Indented)
 printfn "%s"  b

The output of the code is:

{
  "name@": "abc",
  "height@": 200,
  "name": "abc",
  "height": 200
}

How can I avoid the outputs with '@' in the properity?

Answer 1

Try this:

[<CLIMutable>]
[<JsonObject(MemberSerialization=MemberSerialization.OptOut)>]
type T = {
    name : string;
    height : int;
    }

MemberSerialization.OptOut causes only public members to be serialized (skipping private fields which are an implementation detail of records). The CLIMutable attribute is intended specifically for serialization and saves from having to prefix each member with mutable.

Answer 2

With the help of DataMemberAttribute you can specify names of the serialized members:

type T = {
    [<field: DataMember(Name="name")>]
    mutable name : string;
    [<field: DataMember(Name="height")>]
    mutable height : int;
}

Answer 3

Did you try to add attributes [<...>] in front of the property? Because that attribute will only apply to the property, not to the generated backend. Not sure which attribute JSON.NET reacts to, however.