MainViewModel的Binding属性到SubView

Question

我正试图弄清楚如何将MainWindowViewModel中的属性绑定到基于另一个视图的ContentControl。RelativeSource绑定似乎不起作用，因为视图在另一个xaml文件中？我尝试了依赖属性，但我不明白如何正确地做到这一点，我想。

我想在这里实现的是，当我在MainWindow的TextBox中键入时，所有3个视图(内容控件(也会查看更新的数据。它应该是一个演示来说明在MVVM中，ViewModel可以在不知道视图的情况下更改，并且不同的视图会对此做出反应

遗憾的是RelativeSourceBinding和DependencyProperty对我不起作用，或者我错过了一点。

主窗口.xaml

<Window x:Class="MVVMDemo.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<StackPanel>
<TextBlock Text="MVVM Demo" HorizontalAlignment="Center" FontSize="20" FontWeight="Bold"/>
<TextBox Text="{Binding TestString, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Width="200" Background="Black" Foreground="White" Margin="0 20 0 0"/>
<Grid Margin="0 20 0 0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="300"/>
</Grid.RowDefinitions>
<ContentControl Grid.Column="0" Grid.Row="0" Content="{Binding ViewOne}"/>
<ContentControl Grid.Column="1" Grid.Row="0" Content="{Binding ViewTwo}"/>
<ContentControl Grid.Column="2" Grid.Row="0" Content="{Binding ViewThree}"/>
</Grid>

</StackPanel>
</Window>

主窗口视图模型

public class MainWindowViewModel : ViewModelBase
{
/// <summary>
/// String to change the reaction of views
/// </summary>
private string _TestString;
public string TestString
{
get { return _TestString; }
set { _TestString = value; NotifyPropertyChanged(); }
}
private object _ViewOne { get; set; }
public object ViewOne
{
get { return _ViewOne; }
set { _ViewOne = value; NotifyPropertyChanged(); }
}
private object _ViewTwo { get; set; }
public object ViewTwo
{
get { return _ViewTwo; }
set { _ViewTwo = value; NotifyPropertyChanged(); }
}
private object _ViewThree { get; set; }
public object ViewThree
{
get { return _ViewThree; }
set { _ViewThree = value; NotifyPropertyChanged(); }
}
public MainWindowViewModel()
{
ViewOne = new ViewOne();
ViewTwo = new ViewTwo();
ViewThree = new ViewThree();
TestString = "ABC";
}
}

ViewOneViewModel

<UserControl x:Class="MVVMDemo.Views.ViewOne"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
xmlns:local="clr-namespace:MVVMDemo.Views"
mc:Ignorable="d" 
d:DesignHeight="450" d:DesignWidth="800">
<Grid Background="White">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Path=TestString, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Window}}" Foreground="Black"/>
<TextBlock Text="{Binding TestStringProperty}" Foreground="Black"/>
</StackPanel>

</Grid>
</UserControl>

ViewOneViewModel

public class ViewOneViewModel : ViewModelBase
{
// this doesn't help
public static readonly DependencyProperty TestStringProperty =
DependencyProperty.Register("TestString", typeof(string), typeof(MainWindowViewModel), new PropertyMetadata(null));
}

Answer 1

我相信你的问题就在这里：

<TextBlock Text="{Binding Path=TestString, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Window}}" Foreground="Black"/>

Binding Path=TestString应该改为Binding Path=DataContext.TestString，因为RelativeSource现在查看的是窗口，而不是窗口的模型。