Return an object from a popup window

I have a Window which pop-ups another Window. I want the second Window to be able to return an object to the first Window when a button is pressed. How would I do this?

You can expose a property on the second window, so that the first window can retrieve it.

public class Window1 : Window
{
    ...

    private void btnPromptFoo_Click(object sender, RoutedEventArgs e)
    {
        var w = new Window2();
        if (w.ShowDialog() == true)
        {
            string foo = w.Foo;
            ...
        }
    }
}

public class Window2 : Window
{
    ...

    public string Foo
    {
        get { return txtFoo.Text; }
    }

}

If you don't want to expose a property, and you want to make the usage a little more explicit, you can overload ShowDialog:

public DialogResult ShowDialog(out MyObject result)
{
   DialogResult dr = ShowDialog();
   result = (dr == DialogResult.Cancel) 
      ? null 
      : MyObjectInstance;
   return dr;
}

Holy mother of Mars, this took me forever to figure out:

WINDOW 1:

if ((bool)window.ShowDialog() == true)
{
   Window2 content = window.Content as Window2;
   string result = content.result;
   int i = 0;
}

WINDOW 2:

public partial class Window2 : UserControl
{
    public string result
    {
        get { return resultTextBox.Text; }
    }

    public Window2()
    {
        InitializeComponent();
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        Window.GetWindow(this).DialogResult = true;
        Window.GetWindow(this).Close();
    }
}

XAML:

<Button IsDefault="True" ... />

I did it like that.

In parent window make a corresponding ClosingEvent like this :

private void NewWindow_Closing(object sender, System.ComponentModel.CancelEventArgs e)
    {
        NewWindow nw = (NewWindow)sender;

        object Receiver = nw.Sender;
    }

...and in the child window change your code implement the "sender" like this :

    public partial class NewWindow : Window
{
    public object Sender { get; set; }

    public NewWindow()
    {
        InitializeComponent();

        Sender = objectYouWantToSend;
    }
}

So when you put data into the object "Sender" in child window, while closing this window will put the data into the "Receiver" variable.

I hope, this helps.

You can simply call any method of the popup window like this:

int value = 0;
if ((bool)poupWindow.ShowDialog() == true) {
  value = poupWindow.GetValue();
}

I know this is an old one, but I was looking for the same information for a WPF application I'm working on. I found this site to be really helpful:

http://www.dreamincode.net/forums/topic/206458-the-right-way-to-get-values-from-form1-to-form2/

This is written for Windows Forms, but if you ignore the part about passing values to the new window, it still worked and had some really good information.

On a side note, to pass values to the new window, this was really helpful:

https://stackoverflow.com/questions/20547904/wpf-passing-string-to-new-window