Pass Data from Child Window to MainWindow TextBlock

Question

In this example, MainWindow has a button that opens Window2.

Window2 has a button that writes \"Hello, World!\" to MainWindo

Answer 1

You could declare a delegate in Window 2 and pass a function that can be executed when the button is pressed in window 2.

 public delegate void SendMessage(string Message);
 public SendMessage mainWindowDel = null;

Make your constructor that accepts the delegate

 public Window2(SendMessage del)
        {
            mainWindowDel = del;
        }

create window 2 by passing a function as the parameter

 public void showMessage(string Message)
 {
                if(!string.IsNullOrWhiteSpace(Message))
                textBlockMessage.Text = Message;
 }
 private void buttonWindow2_Click(object sender, RoutedEventArgs e)
 {
            // Open Window 2
            //Window2 window2 = new Window2(this);
            Window2 window2 = new Window2(showMessage);
            window2.Left = Math.Max(this.Left - window2.Width, 0);
            window2.Top = Math.Max(this.Top - 0, 0);
            window2.ShowDialog();
  }

call the delegate when they press the button

// Write Message to MainWindow
        private void buttonMessage_Click(object sender, RoutedEventArgs e)
        {
           mainWindowDel("Hello, world!");
        }