Populate (Bind) DropDownList from ViewModel in ASP.Net MVC using MySql

Question

I tried to search posts, without any result either, maybe I didn't use the right words.

I need a solution in MVC for DropDownList will be populated from database using Model class and the Html.DropDownListFor Helper method.

I don't have error on Visual Studio 2019 debug, but the DropDownList is empty.

Please, help me.

My code below

Model

namespace InsGE.Models
{
    public class PersonModel
    {
        public List<SelectListItem> Fruits { get; set; }

        public string Namex { get; set; }
        
        public string Codex { get; set; }

        [Required]
        [Display(Name = "CL")] 
        public string CL { get; set; }

        [Required]
        [Display(Name = "Ticket")]
        public string Ticket { get; set; }
    }
}

Controller

namespace InGE.Controllers
{
    public class HomeController : Controller
    {
        private static List<SelectListItem> PopulateFruits()
        {
            string sql;

            List<SelectListItem> items = new List<SelectListItem>();

            string constr = ConfigurationManager.ConnectionStrings["cn"].ConnectionString;

            using (MySqlConnection con = new MySqlConnection(constr))
            {
                sql = @String.Format("SELECT * FROM `dotable`; ");

                using (MySqlCommand cmd = new MySqlCommand(sql))
                {
                    cmd.Connection = con;
                    con.Open();

                    using (MySqlDataReader sdr = cmd.ExecuteReader())
                    {
                        while (sdr.Read())
                        {
                            items.Add(new SelectListItem
                            {
                                Text = sdr["sName"].ToString(),
                                Value = sdr["sCode"].ToString()
                            });
                        }
                    }
                    con.Close();
                }
            }

            return items;
        }

        [HttpPost]
        public ActionResult Index(PersonModel person)
        {
            string sCl = person.CL;
            string sTicket = person.Ticket;       
            string sName = person.Namex;
            string sCode = person.Codex;

            PersonModel fruit = new PersonModel();
            fruit.Fruits = PopulateFruits();

            return View();
        }

        public ActionResult Index()
        {
            return View();
        }

        public ActionResult About()
        {
            ViewBag.Message = "Your application description page.";

            return View();
        }

        public ActionResult Contact()
        {
            ViewBag.Message = "Your contact page.";

            return View();
        }
    }
}

View

@Html.DropDownListFor(m => m.Fruits, Model.Fruits, "Please select")

Update

Now the debug of Visual Studio 2019 return error

System.Web.Mvc.WebViewPage<TModel>.Model.get 
Object reference not set to an instance of an object error
App_Web_sxdtrbqy

in the view

@Html.DropDownListFor(m => m.Fruits, Model.Fruits, "Please select")

Steve · Accepted Answer · 2020-11-20 22:07:27Z

1

You should populate your model in the Index GET method and then return the model to the View passing it as its parameter.

[HttpGet]
public ActionResult Index()
{
    PersonModel fruit = new PersonModel();
    fruit.Fruits = PopulateFruits();
    return View(fruit);
}

This is the method that will be called when you navigate to the Index page so whatever you put in the model here becomes the model in the view.
The HttpPost method is called when your user push some button or link inside a Form tag to post back the information edited in the View.

edited Nov 20, 2020 at 22:07

answered Nov 20, 2020 at 20:52

Steve

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