Web API complex parameter properties are all null

Question

I have a Web API service call that updates a user's preferences. Unfortunately when I call this POST method from a jQuery ajax call, the request parameter object's properties are always null (or default values), rather than what is passed in. If I call the same exact method using a REST client (I use Postman), it works beautifully. I cannot figure out what I'm doing wrong with this but am hoping someone has seen this before. It's fairly straightforward...

Here's my request object:

public class PreferenceRequest
{
    [Required]
    public int UserId;

    public bool usePopups;
    public bool useTheme;
    public int recentCount;
    public string[] detailsSections;
}

Here's my controller method in the UserController class:

    public HttpResponseMessage Post([FromBody]PreferenceRequest request)
    {
        if (request.systemsUserId > 0)
        {
            TheRepository.UpdateUserPreferences(request.UserId, request.usePopups, request.useTheme,
                                         request.recentCount, request.detailsSections);

            return Request.CreateResponse(HttpStatusCode.OK, "Preferences Updated");                
        }
        else
        {
            return Request.CreateErrorResponse(HttpStatusCode.NotAcceptable, "You must provide User ID");
        }
    }

Here's my ajax call:

var request = {
    UserId: userId,
    usePopups: usePopups,
    useTheme: useTheme,
    recentCount: recentCount,
    detailsSections: details
};

$.ajax({
    type: "POST",
    data: request,
    url: "http://localhost:1111/service/User",
    success: function (data) {
        return callback(data);
    },
    error: function (error, statusText) {
        return callback(error);
    }
});

I've tried setting the dataType & contentType to several different things ('json', 'application/json', etc) but the properties of the request object are always defaulted or null. So, for example, if I pass in this object:

var request = {
  UserId: 58576,
  usePopups: false,
  useTheme: true,
  recentCount: 10,
  detailsSections: ['addresses', 'aliases', 'arrests', 'events', 'classifications', 'custody', 'identifiers', 'phone', 'remarks', 'watches']
}

I can see a fully populated request object with the valid values as listed above. But in the Web API controller, the request is there, but the properties are as follows:

  UserId: 0,
  usePopups: false,
  useTheme: false,
  recentCount: 0,
  detailsSections: null

FYI - I'm not doing ANY ASP.Net MVC or ASP.NET pages with this project, just using the Web API as a service and making all calls using jQuery $.ajax.

Any idea what I'm doing wrong here? Thanks!

UPDATE: I just want to note that I have many methods in this same Web API project in other controllers that do this exact same thing, and I am calling the exact same way, and they work flawlessly! I have spent the morning comparing the various calls, and there doesn't appear to be any difference in the method or the headers, and yet it just doesn't work on this particular method.

I've also tried switching to a Put method, but I get the exact same results - the request object comes in, but is not populated with the correct values. What's so frustrating is that I have about 20 controller classes in this project, and the Posts work in all of those...

Answer 1

This seems to be a common issue in regards to Asp.Net WebAPI.
Generally the cause of null objects is the deserialization of the json object into the C# object. Unfortunately, it is very difficult to debug - and hence find where your issue is.
I prefer just to send the full json as an object, and then deserialize manually. At least this way you get real errors instead of nulls.
If you change your method signature to accept an object, then use JsonConvert:

public HttpResponseMessage Post(Object model)
        {
            var jsonString = model.ToString();
            PreferenceRequest result = JsonConvert.DeserializeObject<PreferenceRequest>(jsonString);
        }

Answer 2

So there are 3 possible issues I'm aware of where the value does not bind:

1. no public parameterless constructor
2. properties are not public settable
3. there's a binding error, which results in a ModelState.Valid == false - typical issues are: non compatible value types (json object to string, non-guid, etc.)

So I'm considering if API calls should have a filter applied that would return an error if the binding results in an error!

Answer 3

Maybe it will help, I was having the same problem.

Everything was working well, and suddently, every properties was defaulted.

After some quick test, I found that it was the [Serializable] that was causing the problem :

public IHttpActionResult Post(MyComplexClass myTaskObject)
{
    //MyTaskObject is not null, but every member are (the constructor get called).
}

and here was a snippet of my class :

[Serializable]  <-- have to remove that [if it was added for any reason..]
public class MyComplexClass()
{
     public MyComplexClass ()
     {
        ..initiate my variables..
     }

     public string blabla {get;set;}
     public int intTest {get;set;
}

Answer 4

I guess problem is that your controller is expecting content type of [FromBody],try changing your controller to

public HttpResponseMessage Post(PreferenceRequest request)

and ajax to

$.ajax({
    type: "POST",
    data: JSON.stringify(request);,
    dataType: 'json',
    contentType: "application/json",
    url: "http://localhost:1111/service/User",

By the way creating model in javascript may not be best practice.

Answer 5

Using this technique posted by @blorkfish worked great:

public HttpResponseMessage Post(Object model)
    {
        var jsonString = model.ToString();
        PreferenceRequest result = JsonConvert.DeserializeObject<PreferenceRequest>(jsonString);
    }

I had a parameter object, which had a couple of native types and a couple more objects as properties. The objects had constructors marked internal and the JsonConvert.DeserializedObject call on the jsonString gave the error:

Unable to find a constructor to use for type ChildObjectB. A class should either have a default constructor, one constructor with arguments or a constructor marked with the JsonConstructor attribute.

I changed the constructors to public and it is now populating the parameter object when I replace the Object model parameter with the real object. Thanks!

Answer 6

I know, this is a bit late, but I just ran into the same issue. @blorkfish's answer worked for me as well, but led me to a different solution. One of the parts of my complex object lacked a parameter-less constructor. After adding this constructor, both Put and Post requests began working as expected.

Answer 7

I have also facing this issue and after many hours from debbug and research can notice the issue was not caused by Content-Type or Type $Ajax attributes, the issue was caused by NULL values on my JSON object, is a very rude issue since the POST neither makes but once fix the NULL values the POST was fine and natively cast to my respuestaComparacion class here the code:

JSON

 respuestaComparacion: {
                            anioRegistro: NULL, --> cannot cast to BOOL
                            claveElector: NULL, --> cannot cast to BOOL
                            apellidoPaterno: true,
                            numeroEmisionCredencial: false,
                            nombre: true,
                            curp: NULL, --> cannot cast to BOOL
                            apellidoMaterno: true,
                            ocr: true
                        }

Controller

[Route("Similitud")]
[HttpPost]
[AllowAnonymous]

public IHttpActionResult SimilitudResult([FromBody] RespuestaComparacion req)
{
   var nombre = req.nombre;
}

Class

public class RespuestaComparacion
    {
        public bool anioRegistro { get; set; }
        public bool claveElector { get; set; }
        public bool apellidoPaterno { get; set; }
        public bool numeroEmisionCredencial { get; set; }
        public bool nombre { get; set; }
        public bool curp { get; set; }
        public bool apellidoMaterno { get; set; }
        public bool ocr { get; set; }
    }

Hope this help.

Answer 8

I came across the same issue. The fix needed was to ensure that all serialize-able properties for your JSON to parameter class have get; set; methods explicitly defined. Don't rely on C# auto property syntax! Hope this gets fixed in later versions of asp.net.

Answer 9

A bit late to the party, but I had this same issue and the fix was declaring the contentType in your ajax call:

    var settings = {
        HelpText: $('#help-text').val(),
        BranchId: $("#branch-select").val(),
        Department: $('input[name=departmentRadios]:checked').val()

    };

$.ajax({
        url: 'http://localhost:25131/api/test/updatesettings',
        type: 'POST',
        data: JSON.stringify(settings),
        contentType: "application/json;charset=utf-8",
        success: function (data) {
            alert('Success');
        },
        error: function (x, y, z) {
            alert(x + '\n' + y + '\n' + z);
        }
    });

And your API controller can be set up like this:

    [System.Web.Http.HttpPost]
    public IHttpActionResult UpdateSettings([FromBody()] UserSettings settings)
    {
//do stuff with your UserSettings object now
        return Ok("Successfully updated settings");
    }

Answer 10

In my case problem was solved when i added

get{}set{}

to parameters class definition:

public class PreferenceRequest
{
    public int UserId;
    public bool usePopups {get; set;}
    public bool useTheme {get; set;}
    public int recentCount {get; set;}
    public string[] detailsSections {get;set;}
}

enstead of:

   public class PreferenceRequest
    {
        [Required]
        public int UserId;
        public bool usePopups;
        public bool useTheme;
        public int recentCount;
        public string[] detailsSections;
    }

Answer 11

As this issue was troubling me for almost an entire working day yesterday, I want to add something that might assist others in the same situation.

I used Xamarin Studio to create my angular and web api project. During debugging the object would come through null sometimes and as a populated object other times. It is only when I started to debug my project in Visual Studio where my object was populated on every post request. This seem to be a problem when debugging in Xamarin Studio.

Please do try debugging in Visual Studio if you are running into this null parameter problem with another IDE.

Answer 12

Today, I've the same problem as yours. When I send POST request from ajax the controller receive empty object with Null and default property values. The method is:

[HttpPost]
public async Task<IActionResult> SaveDrawing([FromBody]DrawingModel drawing)
{


    try
    {

        await Task.Factory.StartNew(() =>
        {
            //Logic
        });
        return Ok();
    }
    catch(Exception e)
    {
        return BadRequest();
    }
}

My Content-Type was correct and everything else was correct too. After trying many things I found that sending the object like this:

$.ajax({
    url: '/DrawingBoard/SaveDrawing',
    type: 'POST',
    contentType: 'application/json',
    data: dataToPost
}).done((response) => { }); 

Won't work, but sending it like this instead worked:

$.ajax({
    url: '/DrawingBoard/SaveDrawing',
    type: 'POST',
    contentType: 'application/json',
    data: JSON.stringify(dataToPost)
}).done((response) => { }); 

Yes, the missing JSON.stringify() caused the whole issue, and no need to put = or anything else as prefix or suffix to JSON.stringify. After digging a little bit. I found that the format of the request payload completely different between the two requests
This is the request payload with JSON.stringify

And this is the request payload without JSON.stringify

And don't forget, when things get magical and you use Google Chrome to test your web application. Do Empty cache and hard reload from time to time.

Answer 13

I ran into the same issue, the solution for me was to make certain the types of my class attributes matched the json atributes, I mean

Json: "attribute": "true"

Should be treated as string and not as boolean, looks like if you have an issue like this all the attributes underneath the faulty attribute will default to null

Answer 14

I ran into the same problem today as well. After trying all of these, debugging the API from Azure and debugging the Xamarin Android app, it turns out it was a reference update issue. Remember to make sure that your API has the Newtonsoft.JSON NUGET package updated (if you are using that).

Answer 15

My issue was not solved by any of the other answers, so this solution is worth consideration:

I had the following DTO and controller method:

public class ProjectDetailedOverviewDto
{
    public int PropertyPlanId { get; set; }

    public int ProjectId { get; set; }

    public string DetailedOverview { get; set; }
}

public JsonNetResult SaveDetailedOverview(ProjectDetailedOverviewDto detailedOverview) { ... }

Because my DTO had a property with the same name as the parameter (detailedOverview), the deserialiser got confused and was trying to populate the parameter with the string rather than the entire complex object. The solution was to change the name of the controller method parameter to 'overview' so that the deserialiser knew I wasn't trying to access the property.

Answer 16

I face this problem this fix it to me

1. use attribute [JsonProperty("property name as in json request")] in your model by nuget package newton
2. if you serializeobject call PostAsync only

like that

var json = JsonConvert.SerializeObject(yourobject);
var stringContent = new StringContent(json, UnicodeEncoding.UTF8, "application/json");
var response = await client.PostAsync ("apiURL", stringContent);

3. if not work remove [from body] from your api

Answer 17

HttpGet

public object Get([FromBody]object requestModel)
{
    var jsonstring = JsonConvert.SerializeObject(requestModel);
    RequestModel model = JsonConvert.DeserializeObject<RequestModel>(jsonstring);
}

Answer 18

  public class CompanyRequestFilterData
    {
             public string companyName { get; set; }
             public string addressPostTown { get; set; }
             public string businessType { get; set; }
             public string addressPostCode{ get; set; }
             public bool companyNameEndWith{ get; set; }
             public bool companyNameStartWith{ get; set; }
             public string companyNumber{ get; set; }
             public string companyStatus{ get; set; }
             public string companyType{ get; set; }
             public string countryOfOrigin{ get; set; }
             public DateTime? endDate{ get; set; }
             public DateTime? startDate { get; set; }
}

webapi controller

    [HttpGet("[action]"),HttpPost("[action]")]
    public async Task<IEnumerable<CompanyStatusVm>> GetCompanyRequestedData(CompanyRequestFilterData filter)
    {}

jsvascript/typescript

export async function GetCompanyRequesteddata(config, payload, callback, errorcallback) {
await axios({
    method: 'post',
    url: hostV1 + 'companydata/GetCompanyRequestedData',
    data: JSON.stringify(payload),
    headers: {
        'secret-key': 'mysecretkey',
        'Content-Type': 'application/json'
    }
})
    .then(res => {
        if (callback !== null) {
            callback(res)
        }
    }).catch(err => {
        if (errorcallback !== null) {
            errorcallback(err);
        }
    })

}

this is the working one c# core 3.1

my case it was bool datatype while i have changed string to bool [companyNameEndWith] and [companyNameStartWith] it did work. so please check the datatypes.