binding

<Window x:Class="WpfApp1.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:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <StackPanel>
        <TextBox x:Name="textBoxName" BorderBrush="Yellow"  Margin="5"/>

        <Button Content =" Add Age" Margin=" 5" Click= "Button_Click"/>
    </StackPanel>

</Window>

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApp1
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    /// 
    /*
    class Student
    {
        private string name;

        public string Name
        {
            get { return name; }

            set { name = value; }

        }

    }
    */
    class Student : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        private string name;

        public string Name1
        {
            get {

                return name;
            }

            set
            {
                name = value;

                if (this.PropertyChanged != null)
                {
                    this.PropertyChanged.Invoke(this, new PropertyChangedEventArgs("Name1"));
                }
            }
                
        }
    }

    public partial class MainWindow : Window
    {
        Student stu;
        public MainWindow()
        {

            InitializeComponent();

            stu = new Student();

            Binding binding = new Binding();

            binding.Source = stu;

            binding.Path = new PropertyPath("Name1");

            BindingOperations.SetBinding(this.textBoxName, TextBox.TextProperty, binding);

        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
         
            stu.Name1 += "Name1";
        }
    }
}