ASP.NET web api cannot get application/x-www-form-urlencoded HTTP POST

I’m new to web-api. I want to receive a HTTP POST data using web-api. The content-type is application/x-www-form-urlencoded, and the request body is like:

data={"mac":"0004ED123456","model":"SG6200NXL"}(JSON format).

My controller is like this:

public void Post([FromBody]string formData)

But formData is always null. Only when I change the request body to:


I can find {"mac":"0004ED123456","model":"SG6200NXL"} was saved in my formData string.

So my question is how should I receive the data with format:


And is there a easy way that I can desalinize the JSON into C#?

Thanks for help!

I tried to use model, but it still not work for me.
My model is:

public class Device
        public string mac { get; set; }
        public string model { get; set; }

and my HTTP POST request is:


User-Agent: Fiddler
Content-type: application/x-www-form-urlencoded
Host: localhost:52154
Content-Length: 46


I have to use Content-type: application/x-www-form-urlencoded as far as I know because the HTTP POST is sent by a router. My job is to receive the data.


Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

Quoting from here:

By default, Web API tries to get simple types from the request URI. The FromBody attribute tells Web API to read the value from the request body.

Web API reads the response body at most once, so only one parameter of an action can come from the request body. If you need to get multiple values from the request body, define a complex type.

Second, the client needs to send the value with the following format:


Specifically, the name portion of the name/value pair must be empty for a simple type.

So, if you want to post data in the format data=string, you have to create complex type.

public class MyFormData
    public string Data { get; set; }

And update your controller like so:
public void Post(MyFormData formData)
    //your JSON string will be in formData.Data

Of course, other alternatives for you is to change the content type to JSON, but really depends on your requirements.

Method 2

This post is old, but I stumbled on it while searching for answer. I’ll post how I got mine to work, maybe someone will find it useful.

Here’s the request:

POST /api/values HTTP/1.1
Host: localhost:62798
Accept: text/json
Content-Type: application/x-www-form-urlencoded
Cache-Control: no-cache
Postman-Token: 51ee1c5f-acbb-335b-35d9-d2b8e62abc74


Here’s the Model:
public class SampleModel{
    public string UID { get; set; }

    public string Email { get; set; }

    public string First_Name { get; set; }

    public string Last_Name { get; set; }

    public string Phone { get; set; }

    public string City { get; set; }

    public string State_Code { get; set; }

    public string Zip { get; set; }

And here’s the POST method that automagically(FromBody) converts urlencoded values to the model.
public HttpResponseMessage Post([FromBody] SampleModel value){

I was able to pick out any value i.e.

Method 3

You should create an object of your data like:

public class Device
  public string mac {get;set;}
  public string model {get;set;}

then change your controller’s action method like this and pass your object to this method from consume
public void Post(Device deviceData)
    // You can extract data like deviceData.mac, deviceData.model etc

You can use one of the popular library for serialize/deserialize of json object in C#

Method 4

create a model

public class MyClass {
    public string mac { get; set; }
    public string model { get; set; }

and use .net JavaScriptSerializer().Deserialize
public void Post([FromBody]string formData){
    MyClass obj = new System.Web.Script.Serialization.JavaScriptSerializer().Deserialize<MyClass>(formData);
    //get mac and model by obj.mac obj.model

cheers 🙂

Method 5

For core 3.x you need to supply the correct decorators to handle the request correctly:

public async Task<IActionResult> MyPostHandler([FromForm] string id)

Method 6

If you are using Content-type: application/x-www-form-urlencoded you can’t expect to receive JSON.

I’m guessing you are using a form to send the data to the Web Api controller?

First you must change the Content-type to application/json and then you must ensure you are sending JSON data in your request body. If you are sending the data via a form, you could use javascript to create a JSON-object out of your form data.

To deserialize JSON in C# i recommend Json.NET:

All methods was sourced from or, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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