Jquery – Data Not Updating, Only Adding Records When EmployeeID is Not Equal to 0

public class EmployeeController : Controller
{
    public ActionResult EmployeeEarnings(int? employeeId)  //GET
    {
        if (employeeId.HasValue)
        {
            using (var dbContext = new EmployeeDbContext())
            {
                var employee = dbContext.EmployeeApplications.Find(employeeId);

                if (employee != null)
                {
                    return View(employee);
                }
            }
        }

        return View(new EmployeeApplication());
    }

    [HttpPost]
    public ActionResult EmployeeEarnings(List<EmployeeApplication> employees)
    {
        try
        {
            if (employees != null && employees.Count > 0)
            {
                using (var dbContext = new EmployeeDbContext())
                {
                    foreach (var employee in employees)
                    {
                        if (!ModelState.IsValid)
                        {
                            var errors = ModelState.Values.SelectMany(v => v.Errors)
                                .Select(e => e.ErrorMessage).ToList();

                            ModelState.Clear();

                            return Json(new { success = false, message = "Validation errors", errors = errors });
                        }

                        if (employee.Id != 0)
                        {
                            var existingEmployee = dbContext.EmployeeApplications.Find(employee.Id);

                            if (existingEmployee != null)
                            {
                                existingEmployee.EmpCode = employee.EmpCode;
                                existingEmployee.EmpName = employee.EmpName;
                                existingEmployee.January = employee.January;
                                existingEmployee.February = employee.February;
                                existingEmployee.March = employee.March;
                                existingEmployee.April = employee.April;
                                existingEmployee.May = employee.May;
                                existingEmployee.June = employee.June;
                            }
                            else
                            {
                                return Json(new { success = false, message = "Employee not found" });
                            }
                        }
                        else
                        {
                            dbContext.EmployeeApplications.Add(employee);
                        }
                    }

                    dbContext.SaveChanges();

                   return Json(new { success = true, message = "Data saved" });
                }
            }
            else
            {
                return Json(new { success = false, message = "No data" });
            }
        }
        catch (Exception ex)
        {
            return Json(new { success = false, message = "Error occurred: " + ex.Message });
        }
    }
}

This is jQuery:

$('#listTable').on('click', '.edit-button', function () {
    var employeeApplicationId = $(this).data('id');
    window.location.href = '/Employee/EmployeeEarnings?employeeId=' + employeeApplicationId;
});

I’m encountering an issue in my code where data is being added instead of updated when the EmployeeID is not equal to 0. I’ve checked my code thoroughly and can’t find the issue.

Can anyone provide some guidance or suggestions on what might be causing this behavior and how to fix it? Thanks in advance!