Deserialize JSON to C# Classes

Question

Below is a (slightly) stripped down response I get from a REST API upon successful creation of a new "job code" entry. I need to deserialize the response into some classes, but I'm stumped.

For reference, I'm using JSON.NET in .NET 3.5 (running in a SSIS script in SQL Server 2008 R2) to attempt my deserialization. Here's the JSON - which I obviously have no control over as it's coming from someone else's API:

{
   "results":{
      "jobcodes":{
         "1":{
            "_status_code":200,
            "_status_message":"Created",
            "id":444444444,
            "assigned_to_all":false,
            "billable":true,
            "active":true,
            "type":"regular",
            "name":"1234 Main Street - Jackson"
         },
         "2":{
            "_status_code":200,
            "_status_message":"Created",
            "id":1234567890,
            "assigned_to_all":false,
            "billable":true,
            "active":true,
            "type":"regular",
            "name":"4321 Some Other Street - Jackson"
         }
      }
   }
}

In my C# code, I do have a "JobCode" class defined which only partially maps the JSON values to properties - I'm not interested in all of the data that's returned to me:

[JsonObject]
class JobCode
{
    [JsonProperty("_status_code")]
    public string StatusCode { get; set; }
    [JsonProperty("_status_message")]
    public string StatusMessage { get; set; }
    [JsonProperty("id")]
    public string Id {get; set;}
    [JsonProperty("name")]
    public string Name { get; set; }

    //-------------------------------------------------------------------------------
    // Empty constructor for JSON serialization support
    //-------------------------------------------------------------------------------

    public JobCode() { }
}

I'm attempting to deserialize the data via this call:

newResource = JsonConvert.DeserializeObject<JobCode>(jsonResponse);

Where jsonResponse is the code outputted above.
When I execute the code, "newResource" always comes back as null - which is not unexpected because I know that there are actually multiple jobcodes in the data and this code is trying to deserialize it into a single JobCode object. I tried creating a new class called "JobCodes" that looks like this:

class JobCodes
{
    [JsonProperty("jobcodes")]
    public List<JobCode>_JobCodes { get; set; }
}

And then I tried calling this:

newResource = JsonConvert.DeserializeObject<JobCodes>(jsonResponse);

But the issue persists - my return object is null. What's throwing me off, I think, is the presence of the "1" and "2" identifiers. I don't know how to account for their presence in my object design and/or usage of the JSON.NET class / property attributes like [JsonObject],[JsonProperty], etc.

When I run the JSON data through JSON2CSharp, it constructs some weird-looking classes, so that hasn't proven too effective. I've validated the JSON with several different validators and it all checks out - I just don't know what I'm missing here.

Ultimately, I'd like to return a List from the JSON data, but I'm stumped on what I need to do to make that happen.

Answer 1

Your problem is twofold:

1. You don't have a class defined at the root level. The class structure needs to match the entire JSON, you can't just deserialize from the middle.
2. Whenever you have an object whose keys can change, you need to use a Dictionary<string, T>. A regular class won't work for that; neither will a List<T>.

Make your classes like this:

class RootObject
{
    [JsonProperty("results")]
    public Results Results { get; set; }
}

class Results
{
    [JsonProperty("jobcodes")]
    public Dictionary<string, JobCode> JobCodes { get; set; }
}

class JobCode
{
    [JsonProperty("_status_code")]
    public string StatusCode { get; set; }
    [JsonProperty("_status_message")]
    public string StatusMessage { get; set; }
    [JsonProperty("id")]
    public string Id { get; set; }
    [JsonProperty("name")]
    public string Name { get; set; }
}

Then, deserialize like this:

RootObject obj = JsonConvert.DeserializeObject<RootObject>(json);

Working demo here

Answer 2

Excellent Answers!

For those out there that may need some more help with the JSON Class Configuration, try: http://json2csharp.com/#

An excellent way of Auto Generating the Classes!

Or even easier, in VS, Goto:

Edit -> Paste Special -> Paste as JSON Classes

Answer 3

Because you can't change the scheme of JSON, and you can't set constant No. of properties, I'd suggest you to use JObject

var jobject = JObject.Parse(json);

var results = jobject["results"];
var jobcodes = results["jobcodes"];

var output = jobcodes.Children<JProperty>()
                     .Select(prop => prop.Value.ToObject<JobCode>())
                     .ToList();

Warning: code assumes, that JSON is always in proper schema. You should also handle invalid schema (for example where property is not of JobCode scheme).

Answer 4

You can also deserialize your json to an object of your target class, and then read its properties as per normal:

var obj = DeSerializeFromStrToObj<ClassToSerialize>(jsonStr);
Console.WriteLine($"Property: {obj.Property}");

where DeSerializeFromStrToObj is a custom class that makes use of reflection to instantiate an object of a targeted class:

    public static T DeSerializeFromStrToObj<T>(string json)
    {
        try
        {
            var o = (T)Activator.CreateInstance(typeof(T));

            try
            {
                var jsonDict = JsonSerializer.Deserialize<Dictionary<string, string>>(json);

                var props = o.GetType().GetProperties();

                if (props == null || props.Length == 0)
                {
                    Debug.WriteLine($"Error: properties from target class '{typeof(T)}' could not be read using reflection");
                    return default;
                }

                if (jsonDict.Count != props.Length)
                {
                    Debug.WriteLine($"Error: number of json lines ({jsonDict.Count}) should be the same as number of properties ({props.Length})of our class '{typeof(T)}'");
                    return default;
                }

                foreach (var prop in props)
                {
                    if (prop == null)
                    {
                        Debug.WriteLine($"Error: there was a prop='null' in our target class '{typeof(T)}'");
                        return default;
                    }

                    if (!jsonDict.ContainsKey(prop.Name))
                    {
                        Debug.WriteLine($"Error: jsonStr does not refer to target class '{typeof(T)}'");
                        return default;
                    }

                    var value = jsonDict[prop.Name];
                    Type t = Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType;
                    object safeValue = value ?? Convert.ChangeType(value, t);
                    prop.SetValue(o, safeValue, null); // initialize property
                }
                return o;
            }
            catch (Exception e2)
            {
                Debug.WriteLine(e2.Message);
                return o;
            }
        }
        catch (Exception e)
        {
            Debug.WriteLine(e.Message);
            return default;
        }
    }

A complete working example class can be found in my enhanced answer to a similar question, here