前台代码

<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="350" Width="525">
    <Grid Name="mygrid">
        <StackPanel>
            <TextBox Text="{Binding mytext}" Width="100" Margin="5"></TextBox>
            <TextBlock Text="{Binding mytext}" Margin="5,0,5,5" Width="100" Background="NavajoWhite"></TextBlock>
            <Button Width="100">click</Button>
        </StackPanel>
    </Grid>
</Window>

后台代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
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;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows.Threading;

namespace WpfApp1
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        private DispatcherTimer dispatcherTimer = null;

        private int i = 0;

        public myClass mcl { get; set; } = new myClass();

        public MainWindow()
        {
            InitializeComponent();
            mcl.mytext = "0";
            mygrid.DataContext = mcl;

            dispatcherTimer = new DispatcherTimer();
            dispatcherTimer.Tick += new EventHandler(TimeCycle);
            dispatcherTimer.Interval = new TimeSpan(0, 0, 0, 0, 1000);
            dispatcherTimer.Start();
        }

        private void TimeCycle(object sender, EventArgs e)
        {
            i += 1;
            mcl.mytext = i.ToString();
        }

        public class myClass : INotifyPropertyChanged
        {
            public event PropertyChangedEventHandler PropertyChanged;
            private string _mytext;
            public string mytext
            {
                get
                { return _mytext; }
                set
                {
                    _mytext = value;
                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("mytext"));
                }
            }
        }
    }
}