Json.NET failes to deserialize Json to a field-only class

Question

I want to parse a piece of JSON with Newtonsoft Json.NET

JSON:

{

    "USER":{
        "result_id":"0",
        "result_description":"NET Connections",
        "cmlog_username":[
            "8118236834",
            "8118236834",
            "8118236834"
        ],
        "caller_id":[
            "14cc20f7b05f",
            "14cc20f7b05f",
            "14cc20f7b05f"
        ]
    }

}

Class

 public class USER
        {
            public string result_id;
            public string result_description;
            public string[] cmlog_username;
            public string[] caller_id;
        }//USER

I convert it with below code but all of property value is NULL

USER con = JsonConvert.DeserializeObject<USER>(msg);

Use properties, not fields. Properties are part of a class' interface while fields are meant to hold internal data only. All serializers work with properties. Fields are always treated as exceptions — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Jun 9, 2016 at 14:22
@PanagiotisKanavos, JSON.NET will happily deserialize into public fields. Here's a fiddle showing it working (dotnetfiddle.net/NNEFMm). — Craig W.
– Craig W., Commented Jun 9, 2016 at 14:30

Craig W. · Accepted Answer · 2016-06-09 14:19:56Z

3

Your deserialization class is incorrect. Putting your JSON into json2csharp.com produces:

public class USER
{
    public string result_id { get; set; }
    public string result_description { get; set; }
    public List<string> cmlog_username { get; set; }
    public List<string> caller_id { get; set; }
}

public class RootObject
{
    public USER USER { get; set; }
}

So you would need to do:

User con = JsonConvert.DeserializeObject<RootObject>(msg);

Your JSON object isn't a USER, it's an object that contains a USER.

answered Jun 9, 2016 at 14:19

Craig W.

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4 Comments

Jack Morton Over a year ago

Upvote, very well explained much better than my answer posted at the same time.

Panagiotis Kanavos Over a year ago

The main difference is that the OP uses fields, while this answer uses properties. While it is possible to deserialize to fields, it's an exceptional case that should be avoided

Craig W. Over a year ago

@PanagiotisKanavos: While it's true that it's more academically correct to use properties it isn't the end of the world if he chooses to use fields.

Panagiotis Kanavos Over a year ago

@CraigW. on the contrary, it is a serious issue. Properties are part of the class's contract. Fields are not, which is why you can't define fields in an interface. Serializers and ORMs expect to find properties, not fields. They require extra configuration to use fields

skalpin · Accepted Answer · 2016-06-09 14:23:06Z

0

It's because the JSON object you are trying to parse into a user is an object that has a property of 'user' that is a user object. That probably didn't make much sense. You could change your json to be

{
    "result_id":"0",
    "result_description":"NET Connections",
    "cmlog_username":[
        "8118236834",
        "8118236834",
        "8118236834"
    ],
    "caller_id":[
        "14cc20f7b05f",
        "14cc20f7b05f",
        "14cc20f7b05f"
    ]
}

and it will work.

answered Jun 9, 2016 at 14:23

skalpin

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Comments

Jack Morton · Accepted Answer · 2016-06-09 14:26:02Z

0

Try adding the get and set to your class

public class USER
{
            public string result_id { get; set; }
            public string result_description { get; set; }
            public string[] cmlog_username { get; set; }
            public string[] caller_id { get; set; }
}//USER

edited Jun 9, 2016 at 14:26

answered Jun 9, 2016 at 14:19

Jack Morton

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3 Comments

Panagiotis Kanavos Over a year ago

These aren't modifiers. The OP uses fields while you show properties. They are different kinds of members, just like a method is different from a field or a property

Jack Morton Over a year ago

Thanks for the clarification @PanagiotisKanavos

Craig W. Over a year ago

@JackMorton: That's not the problem. JSON.NET will deserialize into public fields (dotnetfiddle.net/NNEFMm).

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