Get selected value from HTML.DropDownList back to controller (.Net MVC)

In an MVC application, I have a view showing tasks. Tasks should be filtered by the staff to whom they are assigned. Employees are displayed in the drop-down list.

@using (Html.BeginForm("EmployeeDropUsed", "Task", new { id = ?? }))
{
    @Html.DropDownList(
        "EmployeeDrop", new SelectList(Model.Employees, "Id", "EmployeeName"), "Select employee",
        new
        {
            onchange = @"
            var form = document.forms[0]; 
            form.submit();"
        })
}

I have a TaskController with ActionResult, I take data from the form:

[HttpPost]
public ActionResult EmployeeDropUsed(int id)
{
    Employee e = er.GetById(id);
    return LoadControls(er.GetAll(), e.Tasks.ToList());
}

ViewModel looks like this:

public class TaskModel
{
    public TaskModel(List<Employee> employees, List<Task> tasks)
    {
        Employees = employees;
        Tasks = tasks;
    }

    public List<Task> Tasks { get; set; }
    public List<Employee> Employees { get; set; }
}

The problem is that I do not know how to get the selected value from returning to the controller. I tried using the DropDownListFor and EmployeeId property in the model:

@Html.DropDownListFor(m => Model.EmployeeId, Model.Employees, "Select Employee")

public int EmployeeId { get; set; }

As a result, id is always 0.