WinRT ListView，将itemsource作为列表 <KeyValuePair<string, string> &gt;错误XAML（Windows 8.1通用应用程序（XAML / C＃））

Question

I cant get this to work... (Windows 8 Universal App (XAML/C#) project) I have a listview that is bound to a List < KeyValuePair < string , string > >
here is the code:

                    <ListView 
                       ItemsSource="{Binding Languages}" 
                       SelectedItem="{Binding SelectedLanguage, Mode=TwoWay}"
                       >
                            <ListView.ItemTemplate>
                                <DataTemplate>
                                    <TextBlock Text="{Binding Value}" FontSize="18" FontWeight="Light" />
                                </DataTemplate>
                            </ListView.ItemTemplate>
                        </ListView>

and here is my C# code:

  private List<KeyValuePair<string, string>> _languages;
public List<KeyValuePair<string, string>> Languages
{
    get
    {
        if (_languages == null)
        {
            _languages = Utils.AvailableLanguages;
        }

        return _languages;
    }
}

public KeyValuePair<string, string> SelectedLanguage
{
    get
    {
        return Languages.SingleOrDefault(x => x.Key == Utils.CurrentLanguage);
    }
    set
    {
        Utils.CurrentLanguage = value.Key;
        Api.Localization = value.Key;
        RaisePropertyChanged(() => CurrentLanguage);
    }
}

In my listview if I do a "Binding Value" I get nothing (no data is shown), however if i do Binding without the Value element it shows me both the Key and the Value of my List :

<TextBlock Text="{Binding}" FontSize="18" FontWeight="Light" />

it showns me this:

How do i make it so that i show only the Value of my list and not the key? thank you for your help!

Edit: if i do this:

<TextBlock Text="{Binding key}" FontSize="18" FontWeight="Light"  />

or that

<TextBlock Text="{Binding value}" FontSize="18" FontWeight="Light"  />

same bug, :

Edit2: Utils.AvailableLanguages value:

Answer 1

Try

{Binding key} or {Binding value}

you can reduce code by this

get
{
    return _languages ?? (_languages = Utils.AvailableLanguages);
}

Answer 2

It does indeed seem like the binding can't extract the property values - possibly because the types are generic. This is what you can see in VS Output window:

`A first chance exception of type 'System.Reflection.TargetException' occurred in mscorlib.dll
Error: Cannot get 'Value' value (type 'String') from type 'System.Runtime.InteropServices.WindowsRuntime.CLRIKeyValuePairImpl`2[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. BindingExpression: Path='Value' DataItem='System.Runtime.InteropServices.WindowsRuntime.CLRIKeyValuePairImpl`2[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'; target element is 'Windows.UI.Xaml.Controls.TextBlock' (Name='null'); target property is 'Text' (type 'String').

key and value would be the fields of KeyValuePair while bindings only work with properties, so that wouldn't work. The simple solution is to not use KeyValuePair . You should instead create your own class to hold the language code and country name. If they are both unique - you could simply use a list of strings like this:

XAML

<Page
    x:Class="App51.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Grid
        Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <ListView
            x:Name="lv">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <TextBlock
                        Text="{Binding}"/>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </Grid>
</Page>

C#

using System.Collections.Generic;
using System.Linq;
using Windows.UI.Xaml.Controls;

namespace App51
{
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
            var kvps = new List<KeyValuePair<string, string>>();
            kvps.Add(new KeyValuePair<string, string>("ar", "Argentina"));
            kvps.Add(new KeyValuePair<string, string>("au", "Australia"));
            kvps.Add(new KeyValuePair<string, string>("be-fr", "Belgique"));
            this.lv.ItemsSource = kvps.Select(kvp => kvp.Value).ToList();
        }
    }
}

If there are fewer values than keys - you'd have to do something more like this:

XAML

<Page
    x:Class="App51.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Grid
        Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <ListView
            x:Name="lv">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <TextBlock
                        Text="{Binding Value}"/>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </Grid>
</Page>

C#

using System.Collections.Generic;
using System.Linq;
using Windows.UI.Xaml.Controls;

namespace App51
{
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
            var kvps = new List<KeyValuePair<string, string>>();
            kvps.Add(new KeyValuePair<string, string>("ar", "Argentina"));
            kvps.Add(new KeyValuePair<string, string>("au", "Australia"));
            kvps.Add(new KeyValuePair<string, string>("be-fr", "Belgique"));
            this.lv.ItemsSource = kvps.Select(kvp => new { kvp.Key, kvp.Value }).ToList();
        }
    }
}