Angular2 HTTP Post ASP.NET MVC Web API

Question

How do you properly create a Web API POST of complex object or multiple parameters using Angular2?

I have a service component in Angular2 as seen below:

public signin(inputEmail: string, inputPassword: string): Observable<Response> {
    return this.http.post('/api/account/signin', JSON.stringify({ Email: inputEmail, Password: inputPassword}), this.options);
}

The targeted web api is seen below:

[HttpPost]
[Route("signin")]
public async Task<IActionResult> Signin(string email, string password)
{
       ....
}

This does not work because I need to convert the parameters of the web api into a single POCO class entity with Email and Password properties and put the [FromBody] attribute: Signin([FromBody] Credential credential)

Without using [FromURI] (POST requests with query strings?), how can I make POSTs of multiple parameters or complex objects without converting these parameters into a single POCO class?

Because what if I have numerous Web API POST actions with parameters like (string sensitiveInfo1, string name, int sensitiveInfo2) or (ClassifiedInfo info, string sensitiveInfo1, string sensitiveInfo2), do I need to convert them all to POCO classes and always use [FromBody]?

PS. I was using RestangularJS before and it can posts anything (mulitple primitive objects and complex objects) without my Web API actions having [FromBody] attributes. Will about to investigate how RestangularJS do it.

Answer 1

Without using [FromURI] (POST requests with query strings?), how can I make POSTs of multiple parameters or complex objects without converting these parameters into a single POCO class?

I know its not what you want to hear but out of the box this is not possible. It is not a limitation of the browser code that is making the request. This means it does not matter if you are using Angular, JQuery, straight JavaScript, or even RestangularJS. This is a limitation (I use that word loosely as I am sure this is by design) of Web API (any version). Here is the documentation on this design: Parameter Binding in ASP.NET Web API by Mike Wasson.

At most one parameter is allowed to read from the message body. So this will not work:

// Caution: Will not work!
public HttpResponseMessage Post([FromBody] int id, [FromBody] string name) { ... }

So the question becomes, what are your options?

Create a model

This is the thing you were trying to avoid but I list it first because this is how Web API was intended to behave. I have not yet heard a compelling reason not to do this. This approach allows you to extend your model easily without having to change the method signature. It also allows for model validation on the model itself. Personally I really like this approach.

public class SignInModel{
    public string Email {get;set;}
    public string Password {get;set;}
}

[HttpPost]
[Route("signin")]
public async Task<IActionResult> Signin(SignInModel signInModel)
{
       // ....
}

I did not repeat your existing JavaScript code because what you have works as is with the above web api code

URL

Again, what you were trying to avoid. This does make what you want possible with the limitation that you have to pass these parameters using the Query string on the URL. The JavaScript would change but the signature you had on the Web API method would not.

public signin(inputEmail: string, inputPassword: string): Observable<Response> {
    return this.http.post('/api/account/signin/?email=inputEmail&password=inputPassword', null, this.options);
}

I did not repeat your existing Web API code because what you have works as is with the above web JavaScript code (by default FromUri is assumed I believe)

Custom Model Binder

See Passing multiple POST parameters to Web API Controller Methods by Rick Strahl. This option allows you to create a custom model binder that could do what you are asking. It is a whole bunch of extra code though for, IMHO, not much benefit. Maybe there are situations where it would be useful although I really cannot think of any off the top of my head.

Dynamic

Finally you could also pass in a dynamic object as the parameter of your Web API. This is essentially the same as receiving the JSON as a string and making your Controller code responsible for the deserialization of content. Again, I believe that this would make your code worse in most situations as you have to implement custom validation and type checks. This answer was proposed previously on SO by Bes Ley. Again, maybe there are situations where it would be useful although I really cannot think of any off the top of my head.