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How To Create Asp.net Mvc Dropdownlist With Required Validation

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I working with mvc 5. I am loading data from Database Using ORM and fill a drop down list from the controller, like this. ViewBag.Country_id = new SelectList(_db.Countries, 'Countr

Solution 1:

There are few ways to work with DropDownList. I personally like to use Strongly-Type ViewModel instead of ViewBag.

Screen Shot

Validation message displays when submit button is clicked without selecting Country.

enter image description here

Entity

publicclassCountry
{
    publicint Country_id { get; set; }
    publicstring Description { get; set; }
}

Model

publicclassCountryViewModel
{
    [Display(Name = "Country")]
    [Required(ErrorMessage = "{0} is required.")]
    publicint SelectedCountryId { get; set; }

    public IList<SelectListItem> AvailableCountries { get; set; }

    publicCountryViewModel()
    {
        AvailableCountries = new List<SelectListItem>();
    }
}

Controller

publicclassHomeController : Controller
{
    public ActionResult Create()
    {
        var countries = GetCountries();
        var model = new CountryViewModel {AvailableCountries = countries};
        return View(model);
    }

    [HttpPost]
    publicasync Task<ActionResult> Create(CountryViewModel countryViewModel)
    {
        if (ModelState.IsValid)
        {
            int countryId = countryViewModel.SelectedCountryId;
            // Do something
        }
        // If we got this far, something failed. So, redisplay form
        countryViewModel.AvailableCountries = GetCountries();
        return View(countryViewModel);
    }

    public IList<SelectListItem> GetCountries()
    {
        // This comes from database.var _dbCountries = new List<Country>
        {
            new Country {Country_id = 1, Description = "USA"},
            new Country {Country_id = 2, Description = "UK"},
            new Country {Country_id = 3, Description = "Canada"},
        };
        var countries = _dbCountries
            .Select(x => new SelectListItem {Text = x.Description, Value = x.Country_id.ToString()})
            .ToList();
        countries.Insert(0, new SelectListItem {Text = "Choose a Country", Value = ""});
        return countries;
    }
}

View

@model DemoMvc.Models.CountryViewModel
@{
    Layout = null;
}

<!DOCTYPE html><html><head><metaname="viewport"content="width=device-width" /><title>Create</title></head><body><h2>Create</h2>

    @using (Html.BeginForm())
    {
        <divclass="form-group">
            @Html.LabelFor(model => model.SelectedCountryId, 
               new {@class = "control-label col-md-2"})
            <divclass="col-md-10">
                @Html.DropDownListFor(model => model.SelectedCountryId, 
                    Model.AvailableCountries, new {@class = "form-control"})
                @Html.ValidationMessageFor(model => model.SelectedCountryId, 
                     "", new {@class = "text-danger"})
            </div></div><inputtype="submit"value="Submit"/>
    }

</body></html>

Solution 2:

For .net core instead of @Html.ValidationMessageFor(...

Use

razor cshtml

<spanasp-validation-for="SelectedCountryId"class="text-danger"></span>

model poco

[Required(ErrorMessage = "Country is required.")]
publicint SelectedCountryId { get; set; }

Solution 3:

Model Class

        [Display(Name = "Program")]
        [Required, Range(1, int.MaxValue, ErrorMessage = "Select Program")]
        publicstring Programid { get; set;

View

@Html.DropDownListFor(Model=>Model.Programid,(IEnumerable<SelectListItem>)ViewBag.Program, new {@id = "ddlProgram"})

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