Question

我在MainWindow中有一些UserControl。我试图通过引发UserControl事件并在MainWindow中订阅该事件来在视图之间切换。

我已经看到类似问题的答案，但似乎没有一个对我有帮助。我尝试了下面的代码。运行代码时，placeOrder中的MainWindowViewModel方法被命中，在其中引发PlaceOrderRequested事件。每当引发此事件时，都应调用navigateToOrder中的MainWindowViewModel方法，但不会发生。 MainWindowViewModel中的其他命令被绑定到某些按钮。请帮助我找到问题。

public class CustomerViewModel : ViewModel
{
    public Command<Customer> PlaceOrderCommand { get; }  //uses placeOrder function
    public event Action<Customer> PlaceOrderRequested = delegate {};
    private void placeOrder(Customer cust)
    {//hitting here when put a breakpoint
        PlaceOrderRequested(cust);
    }
}
public class MainWindowViewModel: ViewModel
{
    public Command<string> NavCommand { get; }
    private OrderViewModel orderViewModel = new OrderViewModel();
    private CustomerViewModel customerViewModel = new CustomerViewModel();
    public MainWindowViewModel()
    {
        customerViewModel.PlaceOrderRequested += navigateToOrder;
    }
    private void navigateToOrder(Customer cust)
    {//not hitting here when put a breakpoint
    orderViewModel.Customer = cust;
    CurrentViewModel = orderViewModel;
    }
}
public class ViewModel : INotifyPropertyChanged
{
    protected void OnPropertyChanged(string propName)
    {
        PropertyChanged(this, new PropertyChangedEventArgs(propName));
    }
    public event PropertyChangedEventHandler PropertyChanged = delegate {};
}

这是我的观点，我删除了不必要的行以使代码最少：
MainWindow

<Window x:Class="MVVM_FirstAPP.MainWindow"
        xmlns:local="clr-namespace:MVVM_FirstAPP"
        xmlns:vm="clr-namespace:MVVM_FirstAPP.ViewModels"
        xmlns:views="clr-namespace:MVVM_FirstAPP.Views"
        >
    <Window.Resources>
        <DataTemplate DataType="{x:Type vm:CustomerViewModel}">
            <views:CustomerView></views:CustomerView>
        </DataTemplate>
        <DataTemplate DataType="{x:Type vm:OrderPrepViewModel}">
            <views:OrderPrepView></views:OrderPrepView>
        </DataTemplate>
        <DataTemplate DataType="{x:Type vm:OrderViewModel}">
            <views:OrderView></views:OrderView>
        </DataTemplate>
    </Window.Resources>
    <Window.DataContext>
        <local:MainWindowViewModel />
    </Window.DataContext>
    <Grid>
        <Button Content="Customers"
                HorizontalAlignment="Left"
                Grid.Row="0"
                Command="{Binding NavCommand}"
                CommandParameter="Customer"/>
        <Button Content="OrderPrep"
                Grid.Row="0"
                Command="{Binding NavCommand}"
                CommandParameter="OrderPrep"/>
        <ContentControl Content="{Binding CurrentViewModel}"
                        Grid.Row="1" />
    </Grid>
</Window>

客户视图

<UserControl x:Class="MVVM_FirstAPP.Views.CustomerView"
             xmlns:local="clr-namespace:MVVM_FirstAPP.Views"
             xmlns:customerVM="clr-namespace:MVVM_FirstAPP.ViewModels">
    <UserControl.DataContext>
        <customerVM:CustomerViewModel />
    </UserControl.DataContext>
    <Grid>
        <DataGrid ItemsSource="{Binding Customers}"
                  AutoGenerateColumns="False"
                  SelectedItem="{Binding SelectedCustomer}"
                  Grid.Row="0"
                  CanUserAddRows="False">
            <DataGrid.Columns>
                <DataGridTextColumn Header="ID"
                                    Binding="{Binding Id}"
                                    Width="Auto" />
                <DataGridTextColumn Header="Name"
                                    Binding="{Binding FullName, Mode=OneWay}"
                                    Width="*" />
                <DataGridTemplateColumn Width="Auto">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <!--On Click of this button I want to switch views. This button is calling PlaceOrder command which in turn is raising PlaceOrderRequested event-->
                            <Button Content="Place Order"
                                    Command="{Binding DataContext.PlaceOrderCommand, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"
                                    CommandParameter="{Binding}"/>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</UserControl>

我处于“客户视图”中，当单击“下订单”按钮时，我正在举起placeOrder事件的地方遇到PlaceOrderRequested。 MainWindowViewModel订阅了此活动，但控制权没有得到控制。

MainWindow尚未订阅UserControl的事件

0 个答案: