ASP.NET MVC: how do I call a method and populate a SelectList in a controller?

Question

I need help populating a dropdownlist with values from my model. Below is my code. It is not a Razor Page application so maybe I am missing something.

The controller:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using MappingMVC.Models;

namespace MappingMVC.Controllers
{
    public class CountryController : Controller
    {
        // GET: Country
        [HttpGet]
        public ActionResult Index()
        {
            try
            {
                Countries ctryCountries = new Countries();
                ctryCountries.CountryList = new SelectList(ctryCountries.GetCountries(), "COUNTRYID", "COUNTRYNAME");

                return View(ctryCountries);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                return null;
            }
        }
    }
}

The model

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data;
using System.Data.Entity;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Web.Mvc;

namespace MappingMVC.Models
{
    public class Countries
    {
        private string strCountryCode;
        private string strCountryName;
        private string strCurrencyName;
        private string strCurrencyCode;
        private string strCountryTravelAgentCode;
        private long lCountryID;
        private string strCountrySovereign;
        private string strCountryPhoneCode;
        private DataSet dtCountryDataset;
        private int iCountryAllowedCitizenship;
        private SelectList lsCountryList;

        #region "Properties"

        public string CountryCode
        {
            //USED TO SET AND RETRIEVE THE COUNTRY CODE STRING VALUE
            get { return strCountryCode; }
            set { strCountryCode = value; }
        }

        public string CountryName
        {
            //USED TO SET AND RETRIEVE THE COUNTRY NAME STRING VALUE
            get { return strCountryName; }
            set { strCountryName = value; }
        }

        public string CurrencyName
        {
            //USED TO SET AND RETRIEVE THE CONNECTION STRING VALUE
            get { return strCurrencyName; }
            set { strCurrencyName = value; }
        }

        public string CurrencyCode
        {
            //USED TO SET AND RETRIEVE THE CURRENCY CODE STRING VALUE
            get { return strCurrencyCode; }
            set { strCurrencyCode = value; }
        }

        public string CountryTravelAgentCode
        {
            get { return strCountryTravelAgentCode; }
            set { strCountryTravelAgentCode = value; }
        }

        public long CountryID
        {
            get { return lCountryID; }
            set { lCountryID = value; }
        }

        public string CountryPhoneCode
        {
            get { return strCountryPhoneCode; }
            set { strCountryPhoneCode = value; }
        }

        public string CountrySovereign
        {
            get { return strCountrySovereign; }
            set { strCountrySovereign = value; }
        }

        public DataSet CountryDataset
        {
            //USED TO SET AND RETRIEVE THE COUNTRY CODE STRING VALUE
            get { return dtCountryDataset; }
        }

        // Number of allowed citizenships for citizens of this country
        public int CitizenshipNumberMaximum
        {
            get { return iCountryAllowedCitizenship; }
            set { iCountryAllowedCitizenship = value; }
        }

        public DataSet DataSetCountries
        {
            get { return dtCountryDataset; }
            set { dtCountryDataset = value; }
        }

        public SelectList CountryList 
        {
            get { return lsCountryList; }
            set { lsCountryList = value; }
        }
        #endregion

        // return list of countries
        public IEnumerable<Countries> GetCountries()
        {
            try
            {
                DataSet datCountries;

                MappingLookupsReference.MappingLookupsSoapClient shLookup =
                    new MappingLookupsReference.MappingLookupsSoapClient();

                datCountries = shLookup.ReturnCountryIDAndNamebyCountryName("", 0, 0, 0);

                Countries objCountries = new Countries();
                List<Countries> countryList = new List<Countries>();
                
                countryList = datCountries.Tables[0].AsEnumerable()
                   .Select(dataRow =>
                   new Countries
                   {
                       CountryName = dataRow.Field<string>("COUNTRYNAME"),
                       CountryID = dataRow.Field<int>("COUNTRYID"),
                       CountryCode = dataRow.Field<string>("COUNTRYCODE"),
                       CountryPhoneCode = dataRow.Field<string>("COUNTRYPHONECODE"),
                       CurrencyName = dataRow.Field<string>("CURRENCYNAME"),
                       CurrencyCode = dataRow.Field<string>("CURRENCYCODE"),
                       CountrySovereign = dataRow.Field<string>("COUNTRYSOVEREIGN"),
                       strCountryTravelAgentCode = dataRow.Field<string>("COUNTRYTRAVELAGENTCODE"),
                       iCountryAllowedCitizenship = dataRow.Field<int>("COUNTRYTRAVELAGENTCODE")

                   }).ToList();

                return countryList;
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                return null;
            }
        }
    }
}

The autogenerated view

@model MappingVC.Models.Countries

@{
    ViewBag.Title = "Index";
}

<h2>Index</h2>

<div>
    <h4>Countries</h4>
    <hr />
    <dl class="dl-horizontal">
        <dt>
            @Html.DisplayNameFor(model => model.CountryCode)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.CountryCode)
        </dd>

        <dt>
            @Html.DisplayNameFor(model => model.CountryName)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.CountryName)
        </dd>

        <dt>
            @Html.DisplayNameFor(model => model.CurrencyName)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.CurrencyName)
        </dd>

        <dt>
            @Html.DisplayNameFor(model => model.CurrencyCode)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.CurrencyCode)
        </dd>

        <dt>
            @Html.DisplayNameFor(model => model.CountryTravelAgentCode)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.CountryTravelAgentCode)
        </dd>

        <dt>
            @Html.DisplayNameFor(model => model.CountryID)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.CountryID)
        </dd>

        <dt>
            @Html.DisplayNameFor(model => model.CountryPhoneCode)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.CountryPhoneCode)
        </dd>

        <dt>
            @Html.DisplayNameFor(model => model.CountrySovereign)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.CountrySovereign)
        </dd>

        <dt>
            @Html.DisplayNameFor(model => model.CitizenshipNumberMaximum)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.CitizenshipNumberMaximum)
        </dd>

    </dl>
</div>
<p>
    @Html.ActionLink("Edit", "Edit", new { /* id = Model.PrimaryKey */ }) |
    @Html.ActionLink("Back to List", "Index")
</p>

And finally my dropbox

@model MappingMVC.Models.Countries
@Html.DropDownList("drpdwnCountry", Model.CountryList, "-Select Country-")

Is there something that I am missing to add? How is the GetCountry() method called so as to initiate the Model.CountryList?

When I run the code, the dropdownlist tag gives me the NullReference error in the title of this post.

Thanks for the help in advance.

/James

question from:https://stackoverflow.com/questions/65864748/asp-net-mvc-how-do-i-call-a-method-and-populate-a-selectlist-in-a-controller

Answer 1

Try this:

Fix the action code:

var ctryCountries = new Countries();
ctryCountries.CountryList = new SelectList(ctryCountries.GetCountries(), "CountryID", 
"CountryName");

and fix the dropdown list:

@Html.DropDownListFor(m => m.CountryId, Model.CountryList, "-Select Country-", new { @class = "form-control" })