Xamarin.Forms Picker ItemsSource 在 XAML 中保持为空

Question

My picker stays empty. I already created a test list to test it in particular but it doesn't work either.

this is my XAML

<Picker x:Name="picker1" Grid.Row="1" Grid.Column="1" ItemsSource="{Binding TestList}" ItemDisplayBinding="{Binding Name}" SelectedItem="{Binding AdditionSort}"/>

this is my code behind

List<AdditionSort> TestList
{
    get => testList;
    set => SetValue(ref testList, value);
}

List<AdditionSort> testList = new List<AdditionSort>();

void LoadList()
{
    TestList.Add(new AdditionSort { Name = "test1" });
    TestList.Add(new AdditionSort { Name = "test2" });
}

when I'm debugging I can see that my list is correct.

Answer 1

1)Use System.Generics.ObjectModel.ObservableCollection instead of List .

ObservableCollection notifies View on CollectionChanges where as List doesnot do that.

(Or)

2) Add items to List at initialization of List

List<AdditionSort> testList = new List<AdditionSort>()
{
    new AdditionSort(),
    new AdditionSort(),
    new AdditionSort(),
    new AdditionSort(),
}

Answer 2

I wrote a demo to make the binding work and you can check the code:

In code behind:

public partial class MainPage : ContentPage
{
    public MainPage()
    {
        InitializeComponent();

        myModel m = new myModel();

        BindingContext = m;
    }
}

public class myModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;


    protected virtual void OnPropertyChanged([CallerMemberName]string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    List<AdditionSort> testList = new List<AdditionSort>();

    public List<AdditionSort> TestList
    {
        get { return testList; }
        set
        {
            testList = value;
            OnPropertyChanged();
        }
    }

    public myModel() {

        LoadList();

    }

    void LoadList()
    {
        TestList.Add(new AdditionSort { Name = "test1" });
        TestList.Add(new AdditionSort { Name = "test2" });
    }
}

public class AdditionSort
{       
    public string Name { get; set; }
}

And in Xaml:

<StackLayout>
    <!-- Place new controls here -->
    <Picker x:Name="picker1" ItemsSource="{Binding TestList}" ItemDisplayBinding="{Binding Name}" SelectedItem="{Binding AdditionSort}"/>

</StackLayout>

I uploaded my sample project here .

Also, here is the document: Setting a Picker's ItemsSource Property