How To Validate DropDown List in Asp .net MVC

See more:

MVC

DropDownList

Before Adding the salary of Employee, I had to Select Month from the Drop Down List. The list of the Month are stored in databases. if the month is not selected and user press Create Button the program should display the message that no Month is selected. How Can i achieve this ? If the month is selected and user redirects to create form then the id of the selected month should be stored in (month_id) column of the Salary table. ( i.e month_id = id of the Selected month).

//Model
public class Salary
{
   public int id { get; set; }
   public Nullable<int> month_id { get; set; }

   [Required]
   public virtual Month Month { get; set; }

   public IEnumerable<Month> GetMonths()
   {
        IEnumerable<Month> mat = null;
        mat = this.db.Months.ToList();
        return mat;
   }

}
Public Class Month
{
    public int id { get; set; }
    public string month { get; set; }
    public virtual ICollection<Salary> Salary { get; set; }
}

controller :

public ActionResult Index()
    {
        Salary salary = new Salary();
        ViewData["monthType"] = salary .GetMonths().ToList().Select(
                 s => new SelectListItem
                 {
                     Text = s.month,
                     Value = s.id.ToString()
                 });

        return View(salary);
    }

Views:

@using(Html.BeginForm("Create","Talab",FormMethod.Post))
{ 
    <div class="row">
        <div class="form-group">
            <div class="col-md-2">
                <a href="@Url.Action("Create","TotalSalary")" class="btn btn-success input-sm">Add New </a>
            </div>
        </div>
        <div class="form-group">   
            <div class="col-md-2">
                @Html.DropDownListFor(model => model.Month.id,     (IEnumerable<SelectListItem>)ViewData["monthType"], "--Select a Month--")
                @Html.ValidationMessageFor(model => model.Month.id)
            </div>
        </div>
    </div>
}