Question

How can Web API fail to deserialize an object that JSON.Net deserializes?

This is the Web API controller:

public void Put(EditorSubmissionMainView ajaxSubmission) {
// ajaxSubmission: EditorSubmissionMainView with all values ('data' also == null)

    string json = "{\"id\":\"row_1377\",\"data\":{\"ROTATION\":\"1\",\"EQUIPMENT\":[{\"id\":\"6\"},{\"id\":\"8\"}],\"NOTES\":\"\"}}";

    EditorSubmissionMainView foo = Newtonsoft.Json.JsonConvert.DeserializeObject<EditorSubmissionMainView>(json) as EditorSubmissionMainView;
// foo is a EditorSubmissionMainView but properly deserialized.
}

This is the JSON, captured by Fiddler and formatted:

{
    "id": "row_1377",
    "data": {
        "ROTATION": "1",
        "EQUIPMENT": [{
            "id": "6"
        },
        {
            "id": "8"
        }],
        "NOTES": ""
    }
}

An example class that serializes with JSON.Net but not with a Web API controller:

[Serializable]
public class EditorSubmissionMainView
{
    public string id { get; set; }
    public EditorSubmissionMainViewData data { get; set; }
}

[Serializable]
public class EditorSubmissionMainViewData
{
    [JsonProperty("ROTATION")]
    public int? rotation { get; set; } // Same problem if everything is a string

    [JsonProperty("EQUIPMENT")]
    public ICollection<Dictionary<string, int?>> equipment { get; set; }

    [JsonProperty("NOTES")]
    public string notes { get; set; }
}

Web API uses JSON.Net, and I am not using any custom JSON formatters — just passing the JSON to a Web API controller. Why is this not working?

EDIT:
As requested, I am calling my Web API controller with this Javascript (part of JQuery DataTables). Note that I am certain the same JSON is getting to my controller regardless because I’ve captured the raw HTTP packet with Fiddler and ensured that it is correct:

"ajaxUrl": {
    "create": "POST @Url.Content("~/API/MainView")",
    "edit":   "PUT @Url.Content("~/API/MainView")",
    "remove": "DELETE @Url.Content("~/API/MainView")"
},

"ajax": function (method, url, data, successCallback, errorCallback) {
    $.ajax({
        "type": method,
        "url": url,
        "data": JSON.stringify(data), // Requires IE8+
        "contentType": "application/json",
        "dataType": "json",
        "success": function (json) {
            successCallback(json);
        },
        "error": function (xhr, error, thrown) {
            errorCallback(xhr, error, thrown);
        }
    });
},

The raw HTTP request follows:

PUT http://localhost:53367/API/MainView HTTP/1.1
x-requested-with: XMLHttpRequest
Accept-Language: en-us
Referer: http://localhost:53367/Manage/MainView
Accept: application/json, text/javascript, */*; q=0.01
Content-Type: application/json
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)
Host: localhost:53367
Content-Length: 306
Connection: Keep-Alive
Pragma: no-cache
Cookie: ASP.NET_SessionId=wqsghjrol20cszrxfzdm0qo4

{"id":"row_1377","data":{"ROTATION":"1","EQUIPMENT":[{"id":"6"},{"id":"8"}],"NOTES":""}}

Answer 1

Try removing the [Serializable] attributes from your classes EditorSubmissionMainView and EditorSubmissionMainViewData.