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：

子窗口

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");
        }
    }
}

父窗口

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;
        }
    }
}