Question

我想实现一些消息传递通信（我知道如何使用MVVM.Light的消息传递）但我认为我的情况比较棘手，因为我使用CommandParameter来更改ViewModel，我无法添加命令我想：x让代码变得更清晰。

XAML

<ListView x:Name="dataGrid" ItemsSource="{Binding Friends}" Height="314" BorderThickness="0" SelectedItem="{Binding SelectedItemFriends}">
        <ListView.ItemTemplate>
            <DataTemplate>
                <StackPanel Orientation="Horizontal">
                    <Image Source="Resources\Images\ic_status.png" Height="24" Width="18"/>
                    <StackPanel Margin="5" Orientation="Vertical">
                            <TextBlock FontWeight="Bold" Text="{Binding name}"/>                                
                        <StackPanel x:Name="RemoveItems" Margin="5" Orientation="Vertical">
                            <TextBlock Text="{Binding lastLocation}"/>
                            <TextBlock Text="{Binding timestamp}"/>
                        </StackPanel>
                        <StackPanel x:Name="AdditionItems" Margin="5" Orientation="Vertical" Visibility="Collapsed">
                            <TextBlock Text="{Binding Path=loc.area}"/>
                            <TextBlock Text="{Binding Path=loc.building}"/>
                            <TextBlock Text="{Binding Path=loc.floor}"/>
                            <TextBlock Text="{Binding Path=loc.room}"/>
                        </StackPanel>
                    </StackPanel>
                    <Button Style="{DynamicResource FlatButtonStyle}" Command="{Binding DataContext.SelectViewCommand, ElementName=GeneralWindowView}"  CommandParameter="ChatViewModel" x:Name="button1" Content="Chat" Margin="10">
                        <Button.Template>
                            <ControlTemplate>
                                <Image Source="Resources\Images\chat_image.png"/>
                            </ControlTemplate>
                        </Button.Template>
                    </Button>
                </StackPanel>
                <DataTemplate.Triggers>
                    <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListViewItem}}, Path=IsSelected}" Value="true">
                        <Setter TargetName="AdditionItems" Property="Visibility" Value="Visible"/>
                        <Setter TargetName="RemoveItems" Property="Visibility" Value="Collapsed"/>
                    </DataTrigger>
                </DataTemplate.Triggers>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>

所以我在FriendsViewModel（是GeneralViewModel的孩子）中，我想将信息发送到ChatViewModel（也是GeneralViewModel的孩子）。问题是我可以在哪里发射命令？因为我正在使用命令参数，所以我无法实现其他命令：x并使用messenger。

提前致谢，

编辑：AViewModel

public abstract class AViewModel : ViewModelBase
{
    //public WindowService ws;
    public string Name { get; set; }
    public RelayCommand<string> SelectViewCommand { get; set; }

    public AViewModel()
    {
        //ws = new WindowService();
        SelectViewCommand = new RelayCommand<string>(OnSelectViewCommand);
    }

    private static ObservableCollection<ViewModelBase> _ViewModels;
    public static ObservableCollection<ViewModelBase> ViewModels
    {
        get { return _ViewModels; }
        set { _ViewModels = value; }
    }

    public void AddViewModel(ViewModelBase viewmodel)
    {
        if (ViewModels == null)
            ViewModels = new ObservableCollection<ViewModelBase>();

        var currentVNs = (from vms in ViewModels where vms.InternalName == viewmodel.InternalName select vms).FirstOrDefault();
        if (currentVNs == null)
            ViewModels.Add(viewmodel);
    }

    public ViewModelBase GetViewModel(string viewmodel)
    {
        return ViewModels.FirstOrDefault(item => item.InternalName == viewmodel);
    }
    public ViewModelBase GetViewModelLogin(string viewmodel,object bla)
    {
        return ViewModels.FirstOrDefault(item => item.InternalName == viewmodel);
    }

    private void OnSelectViewCommand(string obj)
    {
        switch (obj)
        {
            case "ExitCommand":
                Application.Current.Shutdown();
                break;
            default:
                this.Current_ViewModel = this.GetViewModel(obj);
                break;
        }
    }

    private ViewModelBase _Current_ViewModel;
    private IMessenger _messengerInstance;

    public ViewModelBase Current_ViewModel
    {
        get { return _Current_ViewModel; }
        set { _Current_ViewModel = value; OnPropertyChanged("Current_ViewModel"); }
    }
    protected IMessenger MessengerInstance
    {
        get
        {
            return this._messengerInstance ?? Messenger.Default;
        }
        set
        {
            this._messengerInstance = value;
        }
    }
}

Answer 1

如果你记得在我上一次演示中，我在AviewModel的属性'Current_ViewModel'的setter中引发了一个'Event'，每次你导航到另一个View时都会被触发。好吧，在考虑之后，我认为事件也可以发送一个对象[到新的ViewModel \ View] ....

你需要使用'CommandParameter'类...... ...

GetSecurityInfo(ph, SE_KERNEL_OBJECT, DACL_SECURITY_INFORMATION, NULL, NULL, &dacl, NULL, &desc)

示例用法...

public enum Command
{
    None,
    LogIn,
    LogOut,
    Recovery,
    Register,
    Exit
}

public class CommandParameter
{
    public dynamic Obj { get; set; }

    public Command Command { get; set; }

    public string Link_1 { get; set; }

    public string Link_2 { get; set; }
}

在上面的代码中

this.LogInCommandParameter = new CommandParameter() { Obj = this.CurrentUser, Command = Command.LogIn, Link_1 = "Main_ViewModel", Link_2 = "LogOnError_ViewModel" };

还有更多内容，所以我在这里添加了另一个演示http://www.mediafire.com/download/5ttjhuiuxex7eo1/Navigation1_25-05.rar（文件大小现在非常大，因为Demo使用EF而且还有一个Web服务......应该都可以工作来自VS IDE tho）

你会在AviewModel中看到

 Obj = the object you want to send onto you next View
 Command = is a 'hint' that you can Switch on in your Buttons bound Command
 Link_1 &  Link_2 are the Views that you want to Navigate too....

我现在正在筹集两个事件（DeActivate和Activate）并且还注意到我发送了一个名为SendObject的参数（这是你在CommandParameter中的Obj）...

在ViewModel中，你只需订阅像这样的事件......

    private ViewModelBase _Current_ViewModel;
    public ViewModelBase Current_ViewModel
    {
        get { return _Current_ViewModel; }
        set {
            if (Current_ViewModel != null)
                Current_ViewModel.RaiseDeActivate(SendObject);
            _Current_ViewModel = value;
            if (Current_ViewModel != null)
                Current_ViewModel.RaiseActivate(SendObject);
            OnPropertyChanged("Current_ViewModel"); }
    }

在演示代码中查看\步骤...您将看到（在创建新用户登录后）一旦您使用有效的UserName \ Password登录，即'User'（整个'User'Object'从LogOn_ViewModel传递到Main_ViewModel通过Base_ViewModel中的OnWindowCommand ...然后在Main_View上显示UserName（你曾经在LogOn_View中登录）。

将ObservableCollection <object> info发送到另一个视图模型

1 个答案: