将一个属性与用户控件拥有的另一个属性绑定

如果你想让你发布的代码尽可能少的改变，那么:

在主窗口。xaml,改变

MyText="{Binding InputText}"

MyText="{Binding RelativeSource={RelativeSource AncestorType=Window}, Path=DataContext.InputText, Mode=TwoWay}"

如果您希望UC更新InputText，则需要two - way。

同样，在MyUserControl.xaml.cs中，在你的DependencyProperty中。在Register语句中，您将字符串的PropertyMetadata默认值设置为0——将其更改为适合字符串的值——例如null或string.empty。

public static readonly DependencyProperty MyTextProperty =
    DependencyProperty.Register("MyText", typeof(string), typeof(MyUserControl), new PropertyMetadata(null));

如果您想稍微改变一下代码，您可以在用户控件中使其更复杂，但在使用时更简单:

使依赖属性MyText在默认情况下以两种方式绑定

停止在用户控件中设置DataContext

更改UC xaml文本绑定以使用UC

我总是发现代码更容易理解，所以这里是你的文件的修改版本:MainWindow.xaml

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:myNS="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="180" Width="300">
    <Grid>
        <StackPanel Orientation="Vertical">
            <TextBlock>
                <Run Text="MainWindow.InputText: " />
                <Run Text="{Binding InputText}" />
            </TextBlock>
            <TextBlock>
                <Run Text="MyUserControl.MyText: " />
                <Run Text="{Binding ElementName=test, Path=MyText}" />
            </TextBlock>
            <myNS:MyUserControl x:Name="test" MyText="{Binding InputText}"></myNS:MyUserControl>
            <Button Name="cmdValidation" Content="Validation" Height="20"></Button>
        </StackPanel>
    </Grid>
</Window>

MainWindow.xaml.cs

using System;
using System.Windows;
using System.ComponentModel;
namespace WpfApplication1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window, INotifyPropertyChanged
    {
        private string inputText = "Initial Value";
        public string InputText
        {
            get { return inputText; }
            set
            {
                inputText = value;
                NotifyPropertyChanged("InputText");
            }
        }
        public MainWindow()
        {
            this.DataContext = this;
            InitializeComponent();
        }
        public event PropertyChangedEventHandler PropertyChanged;
        protected void NotifyPropertyChanged(String property)
        {
            if (this.PropertyChanged != null)
            {
                this.PropertyChanged.Invoke(this, new PropertyChangedEventArgs(property));
            }
        }
    }
}

MyUserControl.xaml

<UserControl x:Class="WpfApplication1.MyUserControl"
             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" 
             mc:Ignorable="d" 
             d:DesignHeight="25 " d:DesignWidth="100"
             Background="Black">
    <Grid>
        <TextBox Height="20" Width="100" Text="{Binding RelativeSource={RelativeSource AncestorType=UserControl}, Path=MyText, UpdateSourceTrigger=PropertyChanged}"></TextBox>
    </Grid>
</UserControl>

MyUserControl.xaml.cs

using System.Windows;
using System.Windows.Controls;
namespace WpfApplication1
{
    /// <summary>
    /// Interaction logic for MyUserControl.xaml
    /// </summary>
    public partial class MyUserControl : UserControl
    {
        public string MyText
        {
            get { return (string)GetValue(MyTextProperty); }
            set { SetValue(MyTextProperty, value); }
        }
        public static readonly DependencyProperty MyTextProperty =
            DependencyProperty.Register("MyText", typeof(string), typeof(MyUserControl), new FrameworkPropertyMetadata(null) { BindsTwoWayByDefault = true });
        public MyUserControl()
        {
            InitializeComponent();
        }
    }
}

首先，

this.DataContext = this;

。只是,没有。您正在覆盖其父窗口设置的UserControl的DataContext。

对于你的UserControl，给它一个x:Name，并直接绑定到依赖属性。

<UserControl
    ...
    x:Name="usr">
    <TextBox Text="{Binding MyText, ElementName=usr}" ... />

完成这些之后，您可以简单地将MyText属性绑定到MainWindow的DataContext。

<myNS:MyUserControl x:Name="test" MyText="{Binding InputText}" />