在视图模型之间传递数据的正确方法是什么? [英] What is the correct way to pass data between view models?

问题描述

我刚刚开始使用 MVVM，我一直在阅读它并做了一些例子.我设法创建了一个应用程序，该应用程序将从数据库中读取然后填充到列表框中.我在尝试将所选项目链接到另一个视图，然后在该视图 viewModel 中进行一些处理时遇到困难.请有人向我解释从 view1 列表框中获取当前所选项目的正确方法，然后在 view2 标签上输出所选项目?

I've just started with MVVM and I have been reading up on it and doing some examples. I've managed to create an application that will read from the database and then populate into a listbox. I am having difficulty in trying to link up the selected item into another view and then do a bit of processing in that views viewModel. Please can somebody explain to me the correct way to get the currently selected item from view1 listbox and then on view2 label just to output the selected item?

这是我的 XAML:

<local:SecondView Margin="499,30,0,20">
        <local:SecondView.DataContext>
            <v:MainViewModel />
        </local:SecondView.DataContext>
    </local:SecondView>
        <Button Height="22" HorizontalAlignment="Left" Margin="8,4,0,0" Name="button1" VerticalAlignment="Top" Width="48" Command="{Binding Path=GetDataCommand}">Button</Button>
    <ListBox ItemsSource="{Binding Path=FileData}"   SelectedItem="{Binding dr}"  Height="330" HorizontalAlignment="Left" Margin="149,30,0,0" Name="listBox1" VerticalAlignment="Top" Width="250" DisplayMemberPath="DDFName" />

这段代码在我的 viewModel1 中:

This piece of code is in my viewModel1:

private DataRowView _dr;
    public DataRowView dr
    {
        get{
            return _dr;
        }

        set
        {
            _dr = value;
            OnPropertyChanged("dr");}
    }

我想以某种方式让 viewModel2 获得 dr 的新值(这是在 view1 列表框中选择的项目)，然后在 view2 上我想显示一些细节

I want to somehow get viewModel2 to get the new value of dr (which is the item selected in view1 listbox) and then on view2 I want to show some details

提前致谢！

推荐答案

您的 ViewModel2 类依赖于 Row --> 在 ViewModel2 中注入依赖项的一种可能性是通过构造函数传递它.

Your ViewModel2 class is depending on the Row --> One possibility to inject the dependency in ViewModel2 is to pass it by constructor.

public class ViewModel1
{
    private DataRowView _dr;
    public DataRowView dr
    {
        get
        {
            return _dr;
        }

        set
        {
            _dr = value;
            OnPropertyChanged("dr");

            this.DetailView = new ViewModel2(value); //On Change of the selected Row create a new viewModel which serves as detail view
        }
    }

    private ViewModel2 _DetailView;
    public ViewModel2 DetailView
    {
        get
        {
            return _DetailView;
        }
        set
        {
            if (_DetailView != value)
            {
                _DetailView = value;
                RaisePropertyChanged(() => this.DetailView);
            }
        }
    }
}

public class ViewModel2
{
    public ViewModel2(DataRowView row)
    {
        this.Row = row;
    }

    private DataRowView _Row;
    public DataRowView Row
    {
        get
        {
            return _Row;
        }
        set
        {
            if (_Row != value)
            {
                _Row = value;
                RaisePropertyChanged(() => this.Row);
            }
        }
    }
}

并且在您的 XAML 中，您可以将数据上下文直接设置为详细信息视图:

and in your XAML you can set the datacontext directly to the detail view:

<local:SecondView Margin="499,30,0,20" DataContext="{Binding DetailView, Mode=OneWay}" />

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