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

Do you set the Content-Type to application/json on the JavaScript request? — Markus
– Markus, Commented Jun 24, 2015 at 9:23
build a javascript object named order with your data and use JSON.stringify while posting. — Amit Kumar Ghosh
– Amit Kumar Ghosh, Commented Jun 24, 2015 at 9:27
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. — Callum Linington
– Callum Linington, Commented Jun 24, 2015 at 9:32

Anton Sizikov · Accepted Answer · 2015-06-24 09:51:10Z

21

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)
{
}

edited Jun 24, 2015 at 9:51

answered Jun 24, 2015 at 9:25

Anton Sizikov

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3 Comments

Amit Kumar Ghosh Over a year ago

contentType in javascript.

Amit Kumar Ghosh Over a year ago

[FromBody] might not be necessary.

vapcguy Over a year ago

@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.

Martin Nilsson · Accepted Answer · 2015-06-24 09:40:23Z

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");

                }
            });
        }

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.

Saveendra Ekanayake · Accepted Answer · 2015-06-24 09:41:15Z

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

edited Jun 24, 2015 at 9:41

answered Jun 24, 2015 at 9:36

Saveendra Ekanayake

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2 Comments

Callum Linington Over a year ago

for WebApi, you should use this attribute [System.Web.Http.HttpPost]

vapcguy Over a year ago

@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:

Arvind Bright · Accepted Answer · 2015-06-24 09:38:56Z

-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.

answered Jun 24, 2015 at 9:38

Arvind Bright

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2 Comments

Amit Kumar Ghosh Over a year ago

this is not an answar.

Eric Wu Over a year ago

Not an answer either.

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