JQUERY ajax posts JSON to C# MVC controller, but the incoming data is null

Question

I have a strange problem. I have a C# data structure with two classes:

public class AddQuestionModel2 { public int? QuestionID { get; set; } public string QuestionString { get; set; } public int? TrueAnswer { get; set; } public QuestionType Type { get; set; } public IEnumerable<AddQuestionModelAnswer> Answers { get; set; } } public class AddQuestionModelAnswer { public int? ID { get; set; } public string AnswerString { get; set; } public bool? IsRight { get; set; } public int? Order { get; set; } } public enum QuestionType { SingleSelect, MultiSelect, OrderAnswers, FillingGap, ExampleRequired, TrueOrFalse } 

The javascript generates the javascript object (which looks fine for the data structure) and JSON.stringify translates to the following json string:

{"QuestionString":"<p>Question 1</p>","TrueAnswer":"0","Type":"0","Answers":[{"AnswerString":"<p>Answer 1</p>","IsRight":"0"},{"AnswerString":"<p>Answer 2</p>","IsRight":"0"},{"AnswerString":"<p>Answer 3</p>","IsRight":"0"},{"AnswerString":"<p>Answer 4</p>","IsRight":"0"}]} 

The json data is sent by the following jquery command:

$.ajax({ url: "/Questions/Add", method: "POST", async: true, dataType: "json", data: JSON.stringify(data), contentType: "application/json; charset=utf-8", success: function (e) { if (e.Success) { document.location = "/Questions"; } }, error: function (e) { var i; for (i in e) { console.log(e[i]); } } }); 

On the C# side, I have the following method to receive the post data:

[HttpPost] public async Task<string> Add([FromBody] AddQuestionModel2 q) { var ctx = this.HttpContext; JsonResultModel res = new JsonResultModel(); } 

The parameter "q" is always null. If I expand ctx (HttpContext), the Request.Form data is threw System.InvalidOperationException.

Does any if you have any idea what could be wrong? The biggest problem is that I am unable to debug what is happening within HttpContext and why it is throwing exception.

Thanks in advance! Gabor

Answer 1

In you ajax code try data:data, instead of data: JSON.stringify(data). The JSON.stringify() method converts a JavaScript object or value to a JSON string, but ajax data need JavaScript object. Another things to try instead of 0 or 1 use "true" or "false" in your bool fields.

In the postman everything works.