Rewriting api and deserializing objects

Question

I am trying to migrate an old api to webapi. Problem is that experience is limited so I am here asking this question.

The current api accepts a json payload in a single url. Say /api . The json payload has the following structure

{'action': 'login', 'username': 'user1', 'password': 'password1'}

This should have been a route like /api/login so I could do something like

[Route("api/Login")]
public string Login(Login login)

and define a class for deserialization like

class Login
{
    public string username{ get; set; }
    public string password{ get; set; }
}

So I made a Route to accept [FromBody] payload and I am stuck finding a way to deserialize the object in a nice way depending on the action.

Every payload could be a valid serializable object with the way I describe If the action key is removed from the payload.

Any suggestions that will not generate ugly code? Please no api rewrite or v2 answer. If I could do it I wouldn't ask this.

Answer 1

Assuming that "action" exists in every payload you could deserialise to the dynamic type then check the action value and then cast the payload again to a specific type once you know what this action is. This addresses the particular issue you are having.

So your endpoint code could look something like this:

//this is written from memory, so could have mistakes ...
var deserialisedData = Newtonsoft.Json.JsonConvert.DeserialiseObject<dynamic>(payload);

switch ( deserialisedData.action )
{
     case "someValue":
          //here you know what the action is so hopefully what kind of payload to              expect
          var properType = payload as SomeProperType
     break;
}

if you were to consider creating a brand new, proper api, you could start introducing endpoints for each action, one at a time. It's much better to separate them than to have one endpoint to rule them all, so to speak.