JSON deserialization using DataContractJsonSerializer

[Andrew]

Hi,

I am using DataContractJsonSerializer to deserialize JSON string in C#
objects but I am having a problem.

Suppose I have a class:

class Item
{
public ItemId Id { get; set; }
}

class ItemId
{
public int Value { get; set; }
}
The JSON string for a Item object looks like this:

{ "Id": 100 }

The deserialization does not work since it expects that Id member is of type
int.
Even if I add a constructor like this:

class ItemId
{
public ItemId(int v)
{
Value = v;
}
public int Value { get; set; }
}

deserialization still doesn't work.

There are some workarounds like chaning the JSON and add Value but I don't
want that.

Is there a way to make deserialization to create the ItemId directly from
int ?

Thaks

[Marc Gravell]

Well, you could use a different member for the serialization?

[DataContract]
class Item {
public ItemId Id {get;set;}

[DataMember(Name="Id")]
private int SerializationId {
get {return Id.Value;}
set {Id = new ItemId(value);}
}
}

That do?

Marc

[Marc Gravell]

What framework are you using? The following (below) works fine for me...

You can always make it public and use [Browsable(false)] and
[EditorBrowsable(EditorBrowsableState.Never)] to make it less visible?

Marc
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Json;
using System.Text;
using System.ComponentModel;
[DataContract]
class Item
{
public ItemId Id { get; set; }

[DataMember(Name = "Id")]
public int SerializationId
{
get { return Id.Value; }
set { Id = new ItemId(value); }
}

static void Main()
{
DataContractJsonSerializer json = new
DataContractJsonSerializer(typeof(Item));
using(MemoryStream ms = new MemoryStream()) {
Item item = new Item { Id = new ItemId(4) };
json.WriteObject(ms, item);
ms.Position = 0;
string txt = Encoding.UTF8.GetString(ms.GetBuffer(), 0,
(int)ms.Length);
item = (Item)json.ReadObject(ms);
System.Console.WriteLine(item.Id.Value);
}
}
}

struct ItemId
{
private readonly int value;
public int Value { get { return value; } }
public ItemId(int value) { this.value = value; }
}

[Andrew]

It works fine for you because you use public access for SerializationId.
Initially you give me the idea to use private and it doesn't work.

Using [Browsable(false)] and [EditorBrowsable(EditorBrowsableState.Never)]
is not an option.

It seems the only option I have is to have 2 public properties which is not
nice.

Thanks.
"Marc Gravell" <ma**********@gmail.comwrote in message
news:ee**************@TK2MSFTNGP04.phx.gbl...

What framework are you using? The following (below) works fine for me...

You can always make it public and use [Browsable(false)] and
[EditorBrowsable(EditorBrowsableState.Never)] to make it less visible?

Marc
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Json;
using System.Text;
using System.ComponentModel;
[DataContract]
class Item
{
public ItemId Id { get; set; }

[DataMember(Name = "Id")]
public int SerializationId
{
get { return Id.Value; }
set { Id = new ItemId(value); }
}

static void Main()
{
DataContractJsonSerializer json = new
DataContractJsonSerializer(typeof(Item));
using(MemoryStream ms = new MemoryStream()) {
Item item = new Item { Id = new ItemId(4) };
json.WriteObject(ms, item);
ms.Position = 0;
string txt = Encoding.UTF8.GetString(ms.GetBuffer(), 0,
(int)ms.Length);
item = (Item)json.ReadObject(ms);
System.Console.WriteLine(item.Id.Value);
}
}
}

struct ItemId
{
private readonly int value;
public int Value { get { return value; } }
public ItemId(int value) { this.value = value; }
}

[Marc Gravell]

>It works fine for you because you use public access

>for SerializationId.

That was actually a hangover from trying the [Browsable] etc. Sorry for
the confusion, but it works fine for me "private" too.

Are you using CF/Silverlight? In regular .NET, DataContractSerializer
(and JSON) works with public *and* non-public members.

Marc

[Andrew]

Oh, okay, I see what you mean now :)
Yes, I am trying to make it work in Silverlight 2 RTM
Is there any way without making both properties public ?
"Marc Gravell" <ma**********@gmail.comwrote in message
news:Oy*************@TK2MSFTNGP02.phx.gbl...

It works fine for you because you use public access
for SerializationId.

That was actually a hangover from trying the [Browsable] etc. Sorry for
the confusion, but it works fine for me "private" too.

Are you using CF/Silverlight? In regular .NET, DataContractSerializer (and
JSON) works with public *and* non-public members.

Marc

[Marc Gravell]

Is there any way without making both properties public ?

At a *push*, maybe a surrogate (IDataContractSurrogate), but I kinda
suspect that it won't exist in Silverlight, and it is also a *lot* of
work. Silverlight is *very* picky about member access / reflection - so
it you want the flat serialization but a structured object model, you
are going to have to compromise with some unsightly (extra) public
properties (ideally with the "hide me" attributes to make them less
annoying).

Marc

[Andrew]

Thanks alot for the insights.
I will have to live with the extra public property and I will try to use the
suggested attributes.

Another (ugly) solution is to have 2 separate objects, internal one for
deserialization and a public one for client use.
The public one will hold inside the internal one and forward properties to
it.

What do you think ?

"Marc Gravell" <ma**********@gmail.comwrote in message
news:%2****************@TK2MSFTNGP06.phx.gbl...

Is there any way without making both properties public ?

At a *push*, maybe a surrogate (IDataContractSurrogate), but I kinda
suspect that it won't exist in Silverlight, and it is also a *lot* of
work. Silverlight is *very* picky about member access / reflection - so it
you want the flat serialization but a structured object model, you are
going to have to compromise with some unsightly (extra) public properties
(ideally with the "hide me" attributes to make them less annoying).

Marc