ASP.NET Core Post Action返回null

Question

I have a simple controller method that should return a JSON result but returns null. I need to call it using jQuery $.ajax . I tested it using Postman and it does return null. I am not sure what I am doing wrong.

I tested it with Postman using the following JSON data and it returns null:

{ "id": 2 }

Here is the controller method:

// Post: Contact
[HttpPost, ActionName("GetContact")]
public JsonResult GetContactPost([FromBody] long id)
{
    var contact = _context.Contact.SingleOrDefault(m => m.ContactId == id);
    return Json(contact);
}

In my application I am using the following JavaScript and it returns null as well:

function GetContact(id) {
    $.ajax({
        type: "POST",
        url: "@Url.Action("GetContact","Contacts")",
        data: { id: id },
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function (result) {
            alert("id: " + id + " result: " + result);
        },
        failure: function (response) {
            alert(response.d);
        }
    });
}

Answer 1

I figured it out. The parameter has to be a model or view model object.

    // Post: Contact
    [HttpPost, ActionName("GetContact")]
    public JsonResult GetContactPost([FromBody] ContactVM findContact)
    {
        var contact = _context.Contact.SingleOrDefault(m => m.ContactId == findContact.Id);
        return Json(contact);
    }