将UserControl属性绑定到Window属性

我正在努力解决一些具有约束力的问题。我有一个带有TextBlock的UserControl。TextBlock的文本绑定到一个属性。在窗口中使用UserControl并用一些文本设置属性时，一切都会按预期进行。但是，当我将该属性绑定到窗口中的另一个属性时，什么也没有发生。这是显示问题的示例：

UserControl xaml：

<UserControl x:Class="TestBinding.UserControl1"
         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="300" d:DesignWidth="300">
<TextBlock Text="{Binding SomeText}"/>

UserControl代码：

public partial class UserControl1 : UserControl
{
    public static readonly DependencyProperty SomeTextProperty = DependencyProperty.Register("SomeText", typeof(string), typeof(UserControl1), new PropertyMetadata("Control Default Text"));

    public string SomeText
    {
        get { return (string)this.GetValue(SomeTextProperty); }
        set { this.SetValue(SomeTextProperty, value); }
    }

    public UserControl1()
    {
        this.DataContext = this;

        InitializeComponent();
    }
}

窗口xaml：

<Window x:Class="TestBinding.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:TestBinding"
    Title="MainWindow" Height="350" Width="525">
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="1*"/>
        <ColumnDefinition Width="1*"/>
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition Height="1*"/>
        <RowDefinition Height="1*"/>
    </Grid.RowDefinitions>
    <local:UserControl1 Grid.Row="0" Grid.Column="0"/>
    <local:UserControl1 Grid.Row="1" Grid.Column="0" SomeText="Another Text" />
    <TextBlock Grid.Row="0" Grid.Column="1" Text="{Binding SomeText}"/>
    <local:UserControl1 Grid.Row="1" Grid.Column="1" SomeText="{Binding SomeText}" />
</Grid>

窗口代码：

public partial class MainWindow : Window
{
    public static readonly DependencyProperty SomeTextProperty = DependencyProperty.Register("SomeText", typeof(string), typeof(MainWindow), new PropertyMetadata("Window Default Text"));

    public string SomeText
    {
        get { return (string)this.GetValue(SomeTextProperty); }
        set { this.SetValue(SomeTextProperty, value); }
    }

    public MainWindow()
    {
        this.DataContext = this;

        InitializeComponent();
    }
}

我希望在右下角看到的是“窗口默认文本”，但得到的是“控件默认文本”。

谢谢你的帮助