How do I get the selected item from a dropdown?

Question

I am writing a Blazor app and my Razor file has a dropdown for Zip Codes. (populated from a CSV file)

Some cities share the same zip code.

Zip, City
00000, CityA
00000, CityB

When I select a city, here is my code

private void SetModel(string zipCode)
{
     var places = places.FirstOrDefault(p => p.ZipCode == zipCode);
     _model.City = place.City;
     _model.State = place.State;
     _model.ZipCode = place.ZipCode;
}

I know FirstOrDefault will always get the first item but I don't know what I should modify the code so I get the User selected item

The code in my Razor file

 <RadzenDropDown Id="locations" AllowFiltering="true" LoadData="@ChangedLocation" Data="@places" TextProperty="Key" ValueProperty="ZipCode" Change="o => SetModel(o.ToString())" />

Answer 1

First I assume you have a model for your zips, at least:

public class Zip
{
    public string ZipCode { get; set; }
}

Using Radzen components this should do the trick in your razor component markup part:

<RadzenDropDown TValue="string" AllowClear="true" AllowFiltering="true" FilterCaseSensitivity="FilterCaseSensitivity.CaseInsensitive" Data="@_zipList" 
            TextProperty="ZipCode" ValueProperty="ZipCode" Change=@(args => OnChange(args)) />

And finally the code part of your component:

List<Zip> _zipList;
List<Place> _places;
SomeModel _model;

protected override void OnInitialized()
{
    _zipList = SomeZipService.GetAll();
    _places = SomePlaceService.GetAll();
}

private void OnChange(object args)
{
    var place = places.FirstOrDefault(p => p.ZipCode == args.ToString());
    _model.City = place.City;
    _model.State = place.State;
    _model.ZipCode = place.ZipCode;
}

Alternatively you can use the bind-Value parameter to bind it to a parameter and not pass anything to the OnChange method.