我有一个ViewModel，其中包含每个子ViewModel中需要的所有属性。 这是我第一次尝试将命令和视图模型拆分为多个文件。上一次，所有内容都在同一个ViewModel中，并且很难使用它。一切都按预期显示，但我想找到一种在每个视图模型中传递相同数据的方法。

从我的GetOrdersCommand中，我想获取HeaderViewModel.SelectedSource属性。我没有找到任何方法来做到没有返回空值或丢失属性数据... 我也想从HeaderView按钮调用我的GetOrdersCommand。

任何提示我如何实现这一目标？也许，我的设计对我想做的事情不好？

MainWindow.xaml

        <views:HeaderView Grid.Row="0" Grid.Column="1" Grid.ColumnSpan="2" DataContext="{Binding HeaderViewModel}" LoadHeaderViewCommand="{Binding LoadHeaderViewCommand}"/>
        <TabControl TabStripPlacement="Bottom" Grid.Row="1" Grid.Column="1" Grid.RowSpan="2" Grid.ColumnSpan="2">
            <TabItem Header="General">
            </TabItem>
            <TabItem Header="Orders">
                <views:OrderView DataContext="{Binding OrderViewModel}" GetOrdersCommand="{Binding GetOrdersCommand}"/>
            </TabItem>
        </TabControl>

HeaderView.xaml

        <DockPanel>
            <ComboBox DockPanel.Dock="Left" Width="120" Margin="4" VerticalContentAlignment="Center" ItemsSource="{Binding SourceList}" SelectedItem="{Binding SelectedSource}" DisplayMemberPath="SourceName"/>
            <Button x:Name="btnTest" HorizontalAlignment="Left" DockPanel.Dock="Left" Margin="4" Content="Test"/>
        </DockPanel>

HeaderView.xaml.cs

    public partial class OrderView : UserControl
    {
        public ICommand GetOrdersCommand
        {
            get { return (ICommand)Getvalue(GetOrdersCommandProperty); }
            set { Setvalue(GetOrdersCommandProperty,value); }
        }
        public static readonly DependencyProperty GetOrdersCommandProperty =
            DependencyProperty.Register("GetOrdersCommand",typeof(ICommand),typeof(OrderView),new PropertyMetadata(null));

        public OrderView()
        {
            InitializeComponent();
        }

        private void UserControl_Loaded(object sender,RoutedEventArgs e)
        {
            if (GetOrdersCommand != null)
            {
                GetOrdersCommand.Execute(this);
            }
        }
    }

MainViewModel.cs

        private OrderViewModel orderViewModel;
        public OrderViewModel OrderViewModel { get; set; } // Getter,setter with OnPropertyChanged

        private HeaderViewModel headerViewModel;
        public HeaderViewModel HeaderViewModel { get; set; } //  Getter,setter with OnPropertyChanged

        public MainViewModel()
        {
            HeaderViewModel = new HeaderViewModel();
            OrderViewModel = new OrderViewModel();
        }

HeaderViewModel.cs

public ICommand LoadHeaderViewCommand { get; set; }
public HeaderViewModel()
{
   LoadHeaderViewCommand = new LoadHeaderViewCommand(this);
}

GetOrdersCommand.cs

    public class GetOrdersCommand : ICommand
    {
        public event EventHandler CanExecuteChanged;
        private readonly OrderViewModel _orderViewModel;

        public GetOrdersCommand(OrderViewModel orderViewModel)
        {
            _orderViewModel = orderViewModel;
        }

        public bool CanExecute(object parameter)
        {
            return true;
        }

        public void Execute(object parameter)
        {
            /* Build Order List according to HeaderViewModel.SelectedSource */
            _orderViewModel.Orders = new ObservableCollection<Order>()
            {
                new Order { ID = 1,IsReleased = false,Name = "Test1"},new Order { ID = 2,IsReleased = true,Name = "Test2"},};
        }
    }