一个用于UserControl和Window的ViewModel或单独的ViewModel

Question

我有MainWindow和AddEdit UserControl.在里面MainWindow我渲染这个AddEdit <Views:AddEditData />,之前这个命名空间被添加到Window元素:

xmlns:Views="clr-namespace:MyProject.WPF.Views"

+++++++++++++++ ++++++++++++++++
ListOfData    + + DataDetails  +
              + +              +
   DataOne    + + Name: txtBox1+
   DataTwo    + +              +
   DataThree  + +              +
              + +  Save data   +
+++++++++++++++ ++++++++++++++++

当用户选择左侧的数据时(例如DataTwo)我想在AddEdit用户控件(DataDetails面板)中显示它的属性(为简单起见,只有Name属性).

由于这UserControl是与MainWindow分开存储的,我应该使用相同的MainWindowViewModel和相同的datacontext,还是应该为AddEdit创建单独的ViewModel UserControl？

希望这听起来很清楚,如果不是,请询问详细信息.

Answer 1

Part 1. Display the properties of the control in MVVM

正如我在评论中所说:

在MVVM中,ViewModel不应该知道所在的控件.在这种情况下,请使用附加的行为或在View中保留相同的侧逻辑

ViewModel与a没有直接关联View,所以只需参考控件的名称就不对了.最好在中设置一个属性Model,并将其绑定到Viewvia中ViewModel,但该属性Name不支持Binding(来自MSDN的引用):

数据绑定名称在技术上是可行的,但是这是一种非常罕见的情况,因为数据绑定名称无法满足属性的主要用途:为代码隐藏提供标识符连接点.

所以我建议使用该Tag属性或Uid.在我的例子中(给出一个下面的),我将Uid属性用于这些目的.

Part 2. Communication via ViewModels (pattern Mediator)

介体模式有几个实施例,但我最喜欢的实现XAML Guy,它简单明了 - 介体模式.

Implementation code

public static class Mediator
{
    static IDictionary<string, List<Action<object>>> pl_dict = new Dictionary<string, List<Action<object>>>();

    static public void Register(string token, Action<object> callback)
    {
        if (!pl_dict.ContainsKey(token))
        {
            var list = new List<Action<object>>();
            list.Add(callback);
            pl_dict.Add(token, list);
        }
        else
        {
            bool found = false;
            foreach (var item in pl_dict[token])
                if (item.Method.ToString() == callback.Method.ToString())
                    found = true;
            if (!found)
                pl_dict[token].Add(callback);
        }
    }

    static public void Unregister(string token, Action<object> callback)
    {
        if (pl_dict.ContainsKey(token))
        {
            pl_dict[token].Remove(callback);
        }
    }

    static public void NotifyColleagues(string token, object args)
    {
        if (pl_dict.ContainsKey(token))
        {
            foreach (var callback in pl_dict[token])
                callback(args);
        }
    }
}

为了展示他的作品,我创建了一个小例子,它由两个组成Views,每个都有自己的ViewModel和Model.

项目结构如下所示:

Output

当您单击Button时,ListOfData ViewModel通过介体与DataDetails进行通信ViewModel,因此:

Mediator.NotifyColleagues("ShowDetails", true);
Mediator.NotifyColleagues("SetSelectedFruit", ListOfDataModel.FruitGreen);

与属性交互的所有过程必须注册ViewModel如下:

private void ShowDetails_Mediator(object args)
{
    bool showDetails = (bool)args;

    if (showDetails == true)
    {
        DataDetailsModel.IsVisible = true;
    }
    else
    {
        DataDetailsModel.IsVisible = false;
    }
}

private void SetSelectedFruit_Mediator(object args)
{
    string selectedFruit = (string)args;

    DataDetailsModel.SelectedFruit = selectedFruit;
}

public DataDetailsViewModel() 
{
    DataDetailsModel = new DataDetailsModel();

    Mediator.Register("ShowDetails", ShowDetails_Mediator);
    Mediator.Register("SetSelectedFruit", SetSelectedFruit_Mediator);
}

在这个例子中我用一个DataTemplate代替UserControl.以下是该项目的主要部分:

MainWindow.xaml

<Window x:Class="CommunicateWithVM.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:ViewModels="clr-namespace:CommunicateWithVM.ViewModels"
    Title="MainWindow" 
    WindowStartupLocation="CenterScreen"
    Height="350"
    Width="525">

    <Grid>
        <ContentControl Name="ListOfData"
                        ContentTemplate="{StaticResource ListOfDataView}">

            <ViewModels:ListOfDataViewModel />            
        </ContentControl>

        <ContentControl Name="DataDetails"
                        ContentTemplate="{StaticResource DataDetailsView}">

            <ViewModels:DataDetailsViewModel />
        </ContentControl>
    </Grid>
</Window> 

Models

DataDetailsModel

public class DataDetailsModel : NotificationObject
{
    #region SelectedFruit

    private string _selectedFruit = "";

    public string SelectedFruit
    {
        get
        {
            return _selectedFruit;
        }

        set
        {
            _selectedFruit = value;
            NotifyPropertyChanged("SelectedFruit");
        }
    }

    #endregion

    #region IsVisible

    private bool _isVisible = false;

    public bool IsVisible
    {
        get
        {
            return _isVisible;
        }

        set
        {
            _isVisible = value;
            NotifyPropertyChanged("IsVisible");
        }
    }

    #endregion
}

ListOfDataModel

public class ListOfDataModel : NotificationObject
{
    #region FruitGreen

    private string _fruitGreen = "Apple";

    public string FruitGreen
    {
        get
        {
            return _fruitGreen;
        }

        set
        {
            _fruitGreen = value;
            NotifyPropertyChanged("FruitGreen");
        }
    }

    #endregion

    #region FruitYellow

    private string _fruitYellow = "Limon";

    public string FruitYellow
    {
        get
        {
            return _fruitYellow;
        }

        set
        {
            _fruitYellow = value;
            NotifyPropertyChanged("FruitYellow");
        }
    }

    #endregion
}

ViewModels

DataDetailsViewModel

public class DataDetailsViewModel
{
    #region DataDetailsModel

    private DataDetailsModel _dataDetailsModel = null;

    public DataDetailsModel DataDetailsModel
    {
        get
        {
            return _dataDetailsModel;
        }

        set
        {
            _dataDetailsModel = value;
        }
    }

    #endregion

    #region ShowDetails_Mediator

    private void ShowDetails_Mediator(object args)
    {
        bool showDetails = (bool)args;

        if (showDetails == true)
        {
            DataDetailsModel.IsVisible = true;
        }
        else
        {
            DataDetailsModel.IsVisible = false;
        }
    }

    #endregion

    #region SetSelectedFruit_Mediator

    private void SetSelectedFruit_Mediator(object args)
    {
        string selectedFruit = (string)args;

        DataDetailsModel.SelectedFruit = selectedFruit;
    }

    #endregion

    #region DataDetailsViewModel Constructor

    public DataDetailsViewModel() 
    {
        DataDetailsModel = new DataDetailsModel();

        Mediator.Register("ShowDetails", ShowDetails_Mediator);
        Mediator.Register("SetSelectedFruit", SetSelectedFruit_Mediator);
    }

    #endregion
}

ListOfDataViewModel

public class ListOfDataViewModel
{
    #region ListOfDataModel

    private ListOfDataModel _listOfDataModel = null;

    public ListOfDataModel ListOfDataModel
    {
        get
        {
            return _listOfDataModel;
        }

        set
        {
            _listOfDataModel = value;
        }
    }

    #endregion

    #region GreenButtonCommand

    private ICommand _greenButtonCommand = null;

    public ICommand GreenButtonCommand
    {
        get
        {
            if (_greenButtonCommand == null)
            {
                _greenButtonCommand = new RelayCommand(param => this.GreenButton(), null);
            }

            return _greenButtonCommand;
        }
    }

    private void GreenButton()
    {
        Mediator.NotifyColleagues("ShowDetails", true);
        Mediator.NotifyColleagues("SetSelectedFruit", ListOfDataModel.FruitGreen);
    }

    #endregion

    #region YellowButtonCommand

    private ICommand _yellowButtonCommand = null;

    public ICommand YellowButtonCommand
    {
        get
        {
            if (_yellowButtonCommand == null)
            {
                _yellowButtonCommand = new RelayCommand(param => this.YellowButton(), null);
            }

            return _yellowButtonCommand;
        }
    }

    private void YellowButton()
    {
        Mediator.NotifyColleagues("ShowDetails", true);
        Mediator.NotifyColleagues("SetSelectedFruit", ListOfDataModel.FruitYellow);
    }

    #endregion

    #region ListOfDataViewModel Constructor

    public ListOfDataViewModel() 
    {
        ListOfDataModel = new ListOfDataModel();
    }

    #endregion
}

Views

DataDetailsView

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                xmlns:ViewModels="clr-namespace:CommunicateWithVM.ViewModels">

    <BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter" />

    <DataTemplate x:Key="DataDetailsView" DataType="{x:Type ViewModels:DataDetailsViewModel}">
        <StackPanel Width="200" 
                    Background="AliceBlue"
                    HorizontalAlignment="Right"
                    Visibility="{Binding Path=DataDetailsModel.IsVisible, 
                                         Converter={StaticResource BooleanToVisibilityConverter}}">

            <TextBlock Text="Fruit: " />
            <TextBlock Text="{Binding Path=DataDetailsModel.SelectedFruit}" />
        </StackPanel>
    </DataTemplate>    
</ResourceDictionary>

ListOfDataView

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:ViewModels="clr-namespace:CommunicateWithVM.ViewModels">

    <DataTemplate x:Key="ListOfDataView" DataType="{x:Type ViewModels:ListOfDataViewModel}">
        <StackPanel Width="200" 
                    Background="Azure"
                    HorizontalAlignment="Left">

            <Button Uid="{Binding Path=ListOfDataModel.FruitGreen}"
                    Content="GreenButton"
                    Command="{Binding Path=GreenButtonCommand}" />

            <Button Uid="{Binding Path=ListOfDataModel.FruitYellow}"
                    Content="YellowButton" 
                    Command="{Binding Path=YellowButtonCommand}" />
        </StackPanel>
    </DataTemplate>    
</ResourceDictionary>

该项目可在此链接中找到.