WPF-Bug：未应用DataTemplates

Question

我有以下问题： 只显示了一个View，其他View没有显示，而是显示了他们的ViewModel，尽管我声明了一些应该替换每个DataTemplate的{​​{1}} ViewModel 1}} - 与它相对应的实例View。 我该如何解决这个问题？

这是我的App.xaml：

<Application x:Class="ThisProgram.App" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" d1p1:Ignorable="d" 
             xmlns:d1p1="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:vm="clr-namespace:ThisProgram.ViewModel"
             xmlns:v="clr-namespace:ThisProgram.View">
  <Application.Resources>
        <ResourceDictionary>
            <DataTemplate DataType="{x:Type vm:PlayerViewModel}">
                <v:PlayerView/>
            </DataTemplate>
            <DataTemplate DataType="{x:Type vm:OperationViewModel}">
                <v:OperationView/>
            </DataTemplate>
            <DataTemplate DataType="{x:Type vm:ChatBoxViewModel}">
                <v:ChatBoxView/>
            </DataTemplate>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Controls.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Fonts.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Colors.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/Orange.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/BaseDark.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>

编辑：添加更多来源

那是我的App.xaml.cs：

    /// <summary>
/// Interaktionslogik für "App.xaml"
/// </summary>
public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);
        // Instanziieren des MainWindows
        MainWindow mainWindow = new MainWindow();
        // Damit wird MainWindow eine Instanz zugewisen, dessen Properties
        // es sich binden kann
        mainWindow.DataContext = MainWindowViewModel.Instance;
        mainWindow.Show();
    }
}

MainWindowViewModel.cs：

 public class MainWindowViewModel : ViewModelBase
{
    private readonly PlayerRepository _playerRepository;
    private readonly OperationRepository _operationRepository;
    private static readonly MainWindowViewModel _instance = new MainWindowViewModel();
    private readonly ObservableCollection<ViewModelBase> _viewModels = new ObservableCollection<ViewModelBase>();

    public static MainWindowViewModel Instance { get { return _instance; } }
    public ObservableCollection<ViewModelBase> ViewModels { get { return _viewModels; } }

    private MainWindowViewModel()
    {
        _playerRepository = new PlayerRepository();
        _operationRepository = new OperationRepository();
        PlayerViewModel playerViewModel = new PlayerViewModel(_playerRepository);
        OperationViewModel operationViewModel = new OperationViewModel(_operationRepository);
        ChatBoxViewModel chatBoxViewModel = new ChatBoxViewModel();
        this.ViewModels.Add(playerViewModel);
        this.ViewModels.Add(operationViewModel);
        this.ViewModels.Add(chatBoxViewModel);
    }
}