Passing ViewModel to Web API controller

Question

Let's say I have two projects in my solution. One is for the front-end. Another one is the back-end. In my front-end project which is built using MVC Web Application, I have this ViewModel. How does my back-end project which is the Web API controller know this ViewModel? Previously with only one project for both front-end and back-end, my code is as below.

public class ChangePinForm
{
    [Range(100000, 999999), Display(Name = "Enter Current Card Pin")]
    [DataType(DataType.Password)]
    public int OldCardPin { get; set; }

    [Range(100000, 999999), Display(Name = "Enter New Card Pin")]
    [DataType(DataType.Password)]
    public int NewCardPin { get; set; }

    [Range(100000, 999999), Display(Name = "Enter New Card Pin Again")]
    [DataType(DataType.Password)]
    public int ConfirmNewCardPin { get; set; }
}

    [HttpPost]
    public ActionResult ChangePin(ChangePinForm changePinForm)
    {
        selectedBankAccount = db.BankAccounts.Find(Session["userid"]);
        if (changePinForm.OldCardPin != selectedBankAccount.PinCode)
        {
            ViewBag.Error = "Please key in the correct current pin number.";
            return View();
        } else if (changePinForm.NewCardPin != changePinForm.ConfirmNewCardPin)
        {
            ViewBag.Error = "New card pin number and Confirm new card pin number do not match.";
            return View();
        } else
        {
            selectedBankAccount.PinCode = changePinForm.ConfirmNewCardPin;
            db.SaveChanges();
            return View("Done");
        }

    }

Answer 1

You can simply receive the object in your API in the back-end, something like

[HttpPost("changepin")]
public ActionResult ChangePin([FromBody] ChangePinForm changePinForm)

This is going to reference ChangePinForm from a separate library (i suggest to use .net standard 2.0) so you can both reference from .net core and .net framework

Answer 2

As Sri Harsha said, you should have your viewmodel class in both solutions.

Alternative, to reduce duplication, you could have a separate class library solely for your model definitions, and reference this class in both projects.