C# - Return variable from child window to parent window in WPF

Question

I have a main window called form1. in form1 I have a button, when it is pressed it will open form2 (form2.ShowDialog()). In form2 I have a button called "Check". When the user clicks on "Check" it should do some validation and if successful creates a string object and return it to form1. Any Ideas on how to implement this? I don't want to return anything when the user closes the window.

Answer 1

Create an event in your second window, have the parameters of the event's delegate contain whatever information you want to pass:

public class Popup : Window
{
    public event Action<string> Check;

    public void Foo()
    {
        //fire the event
        if (Check != null)
            Check("hello world");
    }
}

Then the main window can subscribe to that event to do what it wants with the information:

public class Main : Window
{
    private Label label;
    public void Foo()
    {
        Popup popup = new Popup();
        popup.Check += value => label.Content = value;
        popup.ShowDialog();
    }
}