WPF 中订阅事件没得任何反应

点击按钮没得textBox中内容不发送改变，跟踪后发现PropertyChanged没有起到作用，各位分析下。

这是 dateModel类代码

using System;
using System.ComponentModel;
using System.Windows.Media;

namespace dateModel
{
    public class DateModel:INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler? PropertyChanged;

        private string _value = "我是初始数据，颜色橘色";
        private Brush _valueColor = Brushes.Orange;
        public Brush ValueColor
        {
            get { return _valueColor; }
            set
            {
                _valueColor = value;
                ChangeEVent("ValueColor");//订阅颜色改变
            }
        }
        public string Value
        {  
            get { return _value; }
            set
            {
                _value = value;
                ChangeEVent("Value");//订阅内容改变
                if (value == "我是改变数据，颜色红色") ValueColor = Brushes.Red;
            }
        }
       /// <summary>
       /// 订阅事件
       /// </summary>
       /// <param name="name">事件名称</param>
        private void ChangeEVent( String name)
        {
            if (name != "")
            {
                if (PropertyChanged != null)
                {
                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
                }
            }

        }


    }
}

这是MainWindow代码

using dateModel;
using System.Windows;


namespace test
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

         DateModel? dateModel = null;
        public MainWindow()
        {
            InitializeComponent();
            dateModel = new DateModel();
            this.DataContext = new DateModel();
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            dateModel!.Value = "我是改变数据，颜色红色";
            
        }
    }
}

这是xaml代码

<Window x:Class="test.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"
        xmlns:local="clr-namespace:test" xmlns:datemodel="clr-namespace:dateModel" d:DataContext="{d:DesignInstance Type=datemodel:DateModel}"
        mc:Ignorable="d"
        Title="MainWindow" FontSize="40" Height="450" Width="800">
    <Grid>
        <Button VerticalAlignment="Center" HorizontalAlignment="Right" Width="120" Height="60"  Content="修改" Click="Button_Click"  />
        <TextBox
            VerticalAlignment="Center"
            HorizontalAlignment="Left"
            Width="650"
            Text="{Binding Value}"
            Foreground="{Binding ValueColor}"
           
            />
    </Grid>
</Window>

这段代码马虎了，把第2段 this.DataContext = new DateModel();改为this.DataContext = dateModel;就ok了。