从 IValueConverter 获取对 ViewModel 的引用

public class MyViewModel : INotifyPropertyChanged
{
    private static MyViewModel _instance;

    public MyViewModel()
    {
        _instance = this;
    }

    // ...
}

public class MyValueConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        MyViewModel viewModel = MyViewModel._instance;

        // ...
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        MyViewModel viewModel = MyViewModel._instance;

        // ...
    }
}