save in the database with ajax?

I had an error in txtGafete that prevented entering the ajax below I show the code that I already corrected and functional thanks to everyone for their contributions.

<script>
$(".clMotivo").click(function (event) {
            var id = $(this).attr("data-id");
            var gafete = $("#txtGafete").val();
            var datos = {};
            datos = {
                motivo_Id: $(this).attr("data-id")id,
                gafete: $("#txtGafete").val()
            };
            $.ajax({
                url: "http://localhost:49851/api/visita/agregar",
                method: "POST",
                data: JSON.stringify(datos),
                contentType: "application/json",
                success: function (data) {
                    alert(data);
                    ocultarPopUpAcceso();
                }
            });            
        });
</script>

It's probably because of your url, it's better to work with relative url than to put it completely; in MVC normally controller / function is placed. You can also summarize your data a bit.

<script>
 $(".clMotivo").click(function (event) {
                $.ajax({
                    method: "POST",
                    contentType: "json",
                    url: "/visita/agregar",
                    data: {
                            motivo_Id: $(this).attr("data-id"),
                            gafete: $("txtGafete").val()
                   },
                    success: function (data) {
                        alert(data);
                        ocultarPopUpAcceso();
                    }
                });            
            });
    </script>

Debug your giving a breakpoint on your controller and make sure they are entering the add feature.

You should place the code of the action in the controller that will process the information, only with the JS that you are using is not enough. Your URL link refers to an action in a Controller For example:

public class HomeController: Controller{

   private IDataService servicio;

   public HomeController(IDataService service){
        servicio = service;
   }

   Route["/visita/agregar"]
   public string Post(int motivo_Id, string gafete){
     servicio.guardar(motivo_Id, gafete)
     //retornar mensaje de respuesta al llamado ajax
   }

}

Ideally your controller should not include the logic of saving in database, that would violate the Single Responsibility Principle so you should delegate it to another class. To save in database you have several options. among them this ADO. NET although I recommend you take a look at Dapper.

link

link

I hope it helps you.