webapi无法识别json列表

Question

I've got a list of objects in JSON that isn't recognized by a WebApi2 controller

The JSON list is the following:

{
 "FirstObjectType": [{"Name": "the_name"}], 
 "SecondObjectType": [{"Label": "01_obj"}, {"Label": "02_obj"}]
}

The Model class is:

public class CompositeObject
{
    [JsonProperty("FirstObjectType")]
    public List<FirstObject> fo { get; set; }

    [JsonProperty("SecondObjectType")]
    public List<SecondObject> so { get; set; }
}

The controller is:

public IHttpActionResult PostList([FromBody] CompositeObject jsonList)
{
    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    List<FirstObject> fo_list = jsonList.fo;

    foreach (var item in fo_list)
    {
        db.FirstObject.Add(item);
        db.SaveChanges();
     }

     return StatusCode(HttpStatusCode.OK);
}

When I submit the Post action, the controller recognize both lists in CompositeObject jsonList as Null

Answer 1

There is a problem in your model, where names are not being matched. You have to update model as:

public class FirstObjectType
{
    public string Name { get; set; }
}

public class SecondObjectType
{
    public string Label { get; set; }
}

public class RootObject
{
    public List<FirstObjectType> FirstObjectType { get; set; }
    public List<SecondObjectType> SecondObjectType { get; set; }
}

I have assumed that FirstObjectType contains string with name Name and SecondObjectType contains string with name Label . Make sure to use same names for properties of FirstObjectType and SecondObjectType class as in JSON string.

Answer 2

The issue was in the client code because I missed to set the Content-type as application/json in the header section.
In this way the WebApi server doesn't recognize in the right way the JSON object (I think that the server look for a x-www-form-urlencoded type)

So, the code above is right, but I have found another solution

In the WebApi controller:

using Newtonsoft.Json.Linq;

public IHttpActionResult PostList([FromBody] JObject ReceivedObjectsList)
{           
    var receivedLists = ReceivedObjectsList.Properties();

    List<FirstObject> fo = ReceivedObjectsList["FirstObjectType"].ToObject<List<FirstObject>>();
    List<SecondObject> so = ReceivedObjectsList["SecondObjectType"].ToObject<List<SecondObject>>();

    ...
}