JSON.net Linq and NullValueHandling - linq

Question

Developing a new MVC4 app, I have followed this example on the JSON.net website to fill my viewmodel with a new JSON JObject:
FinalViewModel finalVM= new FinalViewModel();
IList<ResultModel> results = GetResultList();
FinalVM.QueryResults = results;
JObject myJSON = new JObject(
new JProperty("grid",
new JArray(
from g in results
group g by g.ResultYear into y
orderby y.Key
select new JObject {
new JProperty("Year", y.Key),
new JProperty("min_1", y.Min(g=> g.Result_val1)),
new JProperty("min_2", y.Min(g=> g.Result_val2)),
new JProperty("items",
new JArray(
from g in results
where g.ResultYear==y.Key
orderby g.id
select new JObject(
new JProperty("l", g.Result_val1),
new JProperty("j",g.Result_val2),
new JProperty("id", g.id)
)
)
)}
)));
FinalVM.DataJson = myJSON;
return PartialView("_JSONView", FinalVM);
Everything works fine and i get this type of json sent to my view:
{
"grid": [
{
"Year": 1998,
"min_val1": "12",
"min_val2": null,
"items": [
{
"l": 12,
"j": null,
"id": 60
},
{
"l": 25,
"j": null,
"id": 61
}
]
}
]
}
I would like to get rid of the null values when they exist. I read a lot about the NullValueHandling option but do not see how to use it into my Json.Net linq code.

Answer 1

Instead of creating JObjects as part of your LINQ transformation, use anonymous objects. (This will also make your code a heck of a lot more readable!) Afterward, you can load the result object into a JObject using a JsonSerializer instance that has NullValueHandling set to Ignore. This will get rid of the nulls. Here's a demo:
class Program
{
static void Main(string[] args)
{
IList<ResultModel> results = new List<ResultModel>
{
new ResultModel
{
id = 60,
ResultYear = 1998,
Result_val1 = 12,
Result_val2 = null
},
new ResultModel
{
id = 61,
ResultYear = 1998,
Result_val1 = 25,
Result_val2 = null
}
};
var groupedResult = new
{
grid = from g in results
group g by g.ResultYear into y
orderby y.Key
select new
{
Year = y.Key,
min_1 = y.Min(g => g.Result_val1),
min_2 = y.Min(g => g.Result_val2),
items = from g in results
where g.ResultYear == y.Key
orderby g.id
select new
{
l = g.Result_val1,
j = g.Result_val2,
id = g.id
}
}
};
JsonSerializer serializer = new JsonSerializer();
serializer.NullValueHandling = NullValueHandling.Ignore;
JObject myJSON = JObject.FromObject(groupedResult, serializer);
Console.WriteLine(myJSON.ToString(Formatting.Indented));
}
class ResultModel
{
public int id { get; set; }
public int ResultYear { get; set; }
public int? Result_val1 { get; set; }
public int? Result_val2 { get; set; }
}
}
Output:
{
"grid": [
{
"Year": 1998,
"min_1": 12,
"items": [
{
"l": 12,
"id": 60
},
{
"l": 25,
"id": 61
}
]
}
]
}
One other note: if you are not planning to manipulate the JSON, you can actually skip the JObject altogether and serialize your grouped result directly to string instead:
JsonSerializerSettings settings = new JsonSerializerSettings();
settings.NullValueHandling = NullValueHandling.Ignore;
settings.Formatting = Formatting.Indented;
string myJSON = JsonConvert.SerializeObject(groupedResult, settings);