UWP : Bind a Dictionary<string, List<ValidationResult>> to nested controls

Question

C#, UWP

I have a Dictionary<string, List> object and i am trying to bind it to a nested control. but nothing is displayed on screen... I am not sure where i am wrong. here ValidationResult is from System.ComponentModel.DataAnnotations class

public readonly Dictionary<string, List<ValidationResult>> _errors = new Dictionary<string, List<ValidationResult>>();
        public Dictionary<string, List<ValidationResult>> Errors
        {
            get { return _errors; }
        }

Errors.Count does show me some value, but then ItemsControl binding does not produce any results.

 <ItemsControl ItemsSource="{x:Bind VM.Errors , Mode=OneWay}">
                            <ItemsControl.ItemTemplate>
                                <DataTemplate >
                                    <StackPanel>
                                    <TextBlock Text="->" />
                                    <TextBlock Text="{Binding Key}" />
                                        <ListBox ItemsSource="{Binding Value}">
                                            <ListBox.ItemTemplate>
                                                <DataTemplate>
                                                    <StackPanel>
                                                        <TextBlock Text="{Binding ErrorMessage}" />
                                                    </StackPanel>
                                                </DataTemplate>
                                            </ListBox.ItemTemplate>
                                        </ListBox>
                                    </StackPanel>
                                </DataTemplate>
                            </ItemsControl.ItemTemplate>
                        </ItemsControl>

what i am doing wrong, Please advice.

Regards

Answer 1

We can't find you initialize Error dictionary in your page's view model? it could work when I use fake data testing. Please refer the following to check your code.

public class ViewModel
{
    public ViewModel()
    {
        var list = new List<ValidationResult>();
        for (int i = 0; i < 10; i++)
        {
            list.Add(new ValidationResult($"error{i.ToString()}"));

        }
        Errors.Add("section1", list);
    }
    public readonly Dictionary<string, List<ValidationResult>> _errors = new Dictionary<string, List<ValidationResult>>();
    public Dictionary<string, List<ValidationResult>> Errors
    {
        get { return _errors; }
    }
}

Usage

public sealed partial class MainPage : Page
{
    public ViewModel VM { get; set; }
    public MainPage()
    {
        this.InitializeComponent();
        VM = new ViewModel();
    } 
}