Create DropDownListFor from List<myType> - asp.net

Question

I have the following classes:
public class Nationality
{
public int ID { get; set; }
public string name { get; set; }
}
public class PersonalData
{
public List<Nationality> availableNationalities { get; set; }
public PersonalData()
{
availableNationalities = new List<Nationality>();
}
}
In my view, I want to create a DropDownlistFor using the availableNationalities field on the PersonalData.
Follows a piece of view code and an example what I'm trying to do:
#model PersonalData
#Html.DropDownListFor(
model => model.personalData.nationality,
new SelectList(Model.availableNationalities, "ID", "name"),
"Choose please an option",
new { required = "required" }
)
Thank you in advance

Answer 1

Your code will throw an exception as there is no personalData property on your PersonalData view model.
Add one more property in your view model to store the selected option value
public class PersonalData
{
public int SelectedNationality { set;get;}
public List<Nationality> AvailableNationalities { get; set; }
public PersonalData()
{
AvailableNationalities = new List<Nationality>();
}
}
Now in your view you can use the select tag helper (in your ASP.NET Core app)
#model PersonalData
<form asp-controller="Home" asp-action="Create">
<select asp-for="SelectedNationality"
asp-items="#(new SelectList(Model.AvailableNationalities ,"Id","Name"))">
<option>Please select one</option>
</select>
<input type="submit"/>
</form>
If it is a Non core app, you can use the DropDownListFor helper
#Html.DropDownListFor(
a=> a.SelectedNationality,
new SelectList(Model.AvailableNationalities, "ID", "name"),
"Choose please an option",
new { required = "required" }
)
Assuming your GET action method set the AvailableNationalities property on your PersonalData viewmodel object before sending it to the view.
public IActionResult Create()
{
var vm=new PersonalData
{
AvailableNationalities = new List<Nationality>
{
new Nationality { Id=1, Name="USA"},
new Nationality { Id=2, Name="Canada"},
}
};
return View(vm);
}
If all you care about is rendering a SELECT element in the view, you may simply use a List<SelectListItem> instead of List<Nationality> as explained in this post