Confused with FromBody in ASP.NET Core

Question

I have the following WEB API method, and have a SPA template with Angular:

[HttpPost]
public IActionResult Post([FromBody]MyViewModel model)

I thought, based on this topic, there is no need to use [FromBody] here, since I want to read the value from the message body, so there is no need to override the default behavior, but, if I don't use [FromBody], the model that is coming from Angular is null. I'm really confused, why should I use [FromBody], since I have used the default behavior?

Solution 1

For anyone seeing this issue .net core 3 - you need to add the [ApiController] to the controller where you extend ControllerBase. The [FromBody] is only needed if you're doing an MVC controller.

This causes the body to get automatically processed in the way you're expecting.

Microsoft documentation for the ApiController attribute

Solution 2

And here's an alternate approach assuming you need to support both [FromForm] and [FromBody] in your Controller API…

Front-End (Angular Code):

forgotPassword(forgotPassword: ForgotPassword): Observable<number> {
  const params = new URLSearchParams();
  Object.keys(forgotPassword).forEach(key => params.append(key, forgotPassword[key]));
  return this.httpClient.post(`${this.apiAuthUrl}/account/forgotpassword`, params.toString(), { headers: { 'Content-Type': 'application/x-www-form-urlencoded' } });
}

Back-End (C# Code):

[AllowAnonymous]
[HttpPost("[action]")]
public async Task<IActionResult> ForgotPassword(ForgotPasswordViewModel model) { }

Now your signature can remain the same so it can support both.

And another more permanent approach I thought about while addressing.

https://benfoster.io/blog/aspnet-core-customising-model-binding-conventions.

Hope it helps someone!

Comments

[Mathias Haugsbø]

I have seen the same problem in two projects, is there something I missed in the migration documentation from 2.1 -> 2.2 -> 3.0 -> 3.1

[xSx]

are it mean i need add [ApiController] in any route O_o it's so much!(

[duyn9uyen]

I was looking all over for this! Thanks. I have a .NET Core Web API 3.1 project and didn't add [ApiController] to my controller. Then I needed [FromBody]. Added [ApiController] now it works without [FromBody].

[Onur Omer]

I owe you a complete-day! You've saved me!!

[Daniel Frost]

This is not correct. It has to do with which content-type is being used. In order to bind the JSON correctly in ASP.NET Core, you must modify your action to include the attribute [FromBody] on the parameter. This tells the framework to use the content-type header of the request to decide which of the configured IInputFormatters to use for model binding. andrewlock.net/model-binding-json-posts-in-asp-net-core