How to receive JSON data on WebAPI backend C#?

Question

How do I receive JSON data on my WebAPI backend in C#?

I have the following JSON sent from my JavaScript frontend.

{
 "User_Id": 1,
 "TotalPrice": 35,
 "DeliveryAddress": "At my house",
 "CartItems": [
 {
 "Id": 1009,
 "Name": "Superman juni 2014",
 "Quantity": 1,
 "Price": 35
 }
 ]
}

I have this classes:

public class PurchaseOrder
 { 
 public List<CartItem> CartItems { get; set; }
 public string DeliveryAddress { get; set; }
 public int TotalPrice { get; set; }
 public int User_Id { get; set; }
 }
public class CartItem
 {
 public int Id { get; set; }
 public string Name { get; set; }
 public int Quantity { get; set; }
 public int Price { get; set; }
 }

And my WebAPI method:

[System.Web.Mvc.HttpPost]
 public bool AddOrder(PurchaseOrder order)
 {
 // Here I will do something
 return true;
 } 

I only get "null" as the result for my "PurchaseOrder order" object. Can the problem be that I ́m using [System.Web.Mvc.HttpPost]? I have also tried [System.Web.Http.HttpPost], but get the same result. // Martin

• Markus: Do you set the Content-Type to application/json on the JavaScript request?
• DavidG: Can you include the full Javascript request?
• Amit Kumar Ghosh: build a javascript object named order with your data and use JSON.stringify while posting.
• Callum Linington: Unless you're using vNext, this is wrong System.Web.Mvc.HttpPost it should come from the Http namespace I believe not the Mvc one. Secondly this is something to do with your JavaScript.

Answer 1

The Content-Type of your request should be "application/json"

If you post your json in a body of the request than change a method signature to

[HttpPost]
public bool AddOrder([FromBody] PurchaseOrder order)
{
}

• Amit Kumar Ghosh: contentType in javascript.
• Amit Kumar Ghosh: [FromBody] might not be necessary.
• vapcguy: @AmitKumarGhosh No, [FromBody] is mostly assuredly necessary. By default, a WebApiController instance looks in the URL for parameters. If you're using a JSON string and posting that, instead, it has to look in the request body.

Answer 2

Problem solved, it was the "application/json" that was missing. For other persons having the same problem, here is my function. I ́m using Knockout.js, hence the "self"-word.

self.makePurchase = function () {
 var tempUserId = self.orderUserId();
 var tempCartPrice = self.ShoppingCartPrice();
 var tempAddress = self.orderAddress();
 var tempCart = self.ShoppingCart();
 var orderSave = new PurchaseSave(tempUserId, tempCartPrice, tempAddress, tempCart);
 var myData = ko.toJSON(orderSave);
 console.log(myData);
 $.ajax({
 type: "POST",
 async: false,
 url: '/Products/AddOrder',
 contentType: "application/json", // Thank you Stackoverflow!!!
 dataType: "json",
 traditional: true,
 data: myData,
 error: function (xhr, textStatus, errorThrown) {
 console.log(xhr.responseText);
 console.log("Inside the error method");
 },
 success: function (data) {
 console.log("Inside the success method");
 }
 });
 }

• Callum Linington: var self = this is a common thing, just let's you know what this you are referring to as this can change when you are inside say error: function () {} for example.

Answer 3

Change your implementation to this.

[System.Web.Http.HttpPost]
public bool AddOrder([FromBody] PurchaseOrder order)
{
}

For more details - http://www.asp.net/web-api/overview/getting-started-with-aspnet-web-api/tutorial-your-first-web-api

• Callum Linington: for WebApi, you should use this attribute [System.Web.Http.HttpPost]
• vapcguy: @SaveendraEkanayake Looks like you were typing up this response at the same time as Anton & just submitted it 11 mins after he did... But it's basically the same thing-at least you have a link. Missed the part about the Content-Type.. but it didn't help that the OP didn't post his JavaScript - if he had, I'm sure you would've caught that, though. :wink:

Answer 4

Try using Newtonsoft.Json package from NuGet. They have functions to serialize and deserialize any string to Json. Also try using dynamic type variables. Helps for deserializing.

• Amit Kumar Ghosh: this is not an answar.
• Eric Wu: Not an answer either.