Question

In a MVC application, I have a view showing tasks. The tasks should be filtered by employees to which they are assigned. Employees are shown in a dropdownlist.

@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 an ActionResult, taking the data from the form:

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

The 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 I don´t know how to get the selected value from the drop back to the controller. I tried using DropDownListFor and an EmployeeId property in the model:

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

public int EmployeeId { get; set; }

The result is that id is always 0.

Answer 1

The problem is that your EmployeeDropUsed action is looking for a parameter named id and the parameter you are sending it is EmployeeId. Either change the parameter name on the EmployeeDropUsed action to employeeId or change the EmployeeId property on TaskModel to id.

If you change the TaskModel property this should work:

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

If you change the EmployeeDropUsed parameter this should work:

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