Rest API- how to get json API request call and send json response using C#?

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C#

My requirements are

1.create API to get the user information(JSON request as given in below) from other system, update those information to database.
2.After update want to send the JSON response(model is given below) back.


I'm using entity framework model. I want to build the API to meet the mentioned requirements, please help me

My controller:

namespace CT.API.User
{
    public class UserController : CTControllerBase
    {
        //API
        [AllowAnonymous]
        public JsonResult USerApiTest()
        {
            // to handle the code
       }
    }
}

Request Details:

{"REQLEN":4,"REQDTL":[{"ID":"48490","UserName":"Test1","Password":"Test1"},{"ID":"48491","UserName":"Test2","Password":"Test2"}]}

Reponse Details:

{"RESLEN":4,"RESDTL":[{"ID":"48490","Status":"Success"},{"ID":"48491","Status":"Fail"}]}

What I have tried:

I'm new to API and want to build the API to meet the mentioned requirements, please help me with the code