CODEWITHSUNDEEP
c#jsondynamicjson.netnullable
Anduril
Anduril

Reputation: 1276

Json.Net can't deserialize from dynamic object to nullable<short>

I have the following JSON being sent to an MVC controller:

{
  "CId": 374,
  "CultureId": 1,
  "VGS": null,
  "DisplayOrder": 1
}

I am using JSON.Net to convert this to a dynamic object and later assigning the properties into an entity:

public partial class FooEntity
{
    public short DisplayOrder { get; set; }
    public Nullable<short> VGS { get; set; }
    public short CId { get; set; }
    public short CultureId { get; set; }
}

Notice that the VGS property we are assigning into is a nullable short, however when trying to create a new instance of the entity and assign the values, I get an error when trying to assign the VGS:

dynamic data = JsonConvert.DeserializeObject(payload);
var foo = new FooEntity();
foo.CId = data.CId;
foo.CultureId = data.CultureId;
foo.VGS = data.VGS; // Errors here
foo.DisplayOrder = data.DisplayOrder;

An exception of type 'System.FormatException' occurred in mscorlib.dll but was not handled in user code

Additional information: Input string was not in a correct format.

As far as I can tell, the json is correct to deserialize into a null value, and since I am assigning into a nullable value, I'm not sure what is causing the error?

Upvotes: 2

Views: 507

Answers (1)

smoksnes
smoksnes

Reputation: 10851

JSON.Net does not know what to parse VGS to, which will make it an object. Then you cannot assign an object to VGS. Below is a working example. It can be solved in several ways:

Solution 1: Use explicit cast.

var payload = "{\"CId\": 374, \"CultureId\": 1,\"VGS\": null,\"DisplayOrder\": 1}";
dynamic dyn = JsonConvert.DeserializeObject<FooEntity>(payload);
var foo2 = new FooEntity();
foo.CId = dyn.CId;
foo.CultureId = dyn.CultureId;
foo.VGS = (short?)dyn.VGS; // Note the explicit cast.
foo.DisplayOrder = dyn.DisplayOrder;

Solution 2: Specify type.

var payload = "{\"CId\": 374, \"CultureId\": 1,\"VGS\": null,\"DisplayOrder\": 1}";
dynamic data = JsonConvert.DeserializeObject<FooEntity>(payload); // Specify type.
var foo = new FooEntity();
foo.CId = data.CId;
foo.CultureId = data.CultureId;
foo.VGS = data.VGS;
foo.DisplayOrder = data.DisplayOrder;

But then there's really no reason to use dynamic at all. You can serialize it directly to the entity you want.

FooEntity entity = JsonConvert.DeserializeObject<FooEntity>(payload);

Upvotes: 1

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