利用委托让子窗口操作父窗口或传值

思路如下：

首先在子窗口定义委托和事件，然后在父窗口调用子窗口时订阅事件，并在事件中写入想让子窗口操作父窗口或传值的具体内容。

代码如下：

namespace WpfApplicationTest
{
    //定义委托
    public delegate void ChangeTextHandler(string text);
    /// <summary>
    /// chrild.xaml 的交互逻辑
    /// </summary>
    
    public partial class chrild : Window
    {
        //定义事件
        public event ChangeTextHandler ChangeTextEvent;
        public chrild()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            ChangeTextEvent("mychange");
        }

        private void Window_Closed(object sender, EventArgs e)
        {
            ChangeTextEvent("closed");
        }
    }
}

namespace WpfApplicationTest
{
    /// <summary>
    /// father.xaml 的交互逻辑
    /// </summary>
    public partial class father : Window
    {
        public father()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            chrild ch = new chrild();
            //订阅事件
            ch.ChangeTextEvent += new ChangeTextHandler(ch_ChangeTextEvent);
            ch.Show();
        }

        void ch_ChangeTextEvent(string text)
        {
            //让子窗口操作父窗口或传值的具体内容
            this.textBlock1.Text = text;
        }
    }
}