How to pass data to the previous page using PopAsync?

Question

Consider the following scenario:

1. User is on some Page 1
2. He clicks button that moves him to Page 2 (calling await Navigation.PushAsync(new SomePage()); )
3. After finishing certain action, he clicks "OK" button
4. After clicking "OK", app calls PopAsync to move to Page 1 and sends there some data (result of activity on Page 2).

How can I receive data from Page 2 in Page 1?

Answer 1

The best way (IMO) would be to handle the pop from the originating page by raising an event. Something like this:

public class LoginPage : ContentPage
{
    public event EventHandler LoginSucceeded;

    public event EventHandler LoginFailed;

    private void OnLoginSucceeded()
    {
        if (LoginSucceeded != null)
        {
            LoginSucceeded(this, EventArgs.Empty);
        }
    }

    private void OnLoginFailed()
    {
        if (LoginFailed != null)
        {
            LoginFailed(this, EventArgs.Empty);
        }
    }
}

and from app.cs

public class App : Application
{
    public App()
    {
        var loginPage = new LoginPage();
        loginPage.LoginSucceeded += HandleLoginSucceeded;
        MainPage = loginPage;
    }

    private void HandleLoginSucceeded(object sender, EventArgs e)
    {
        MainPage = new MainPage();
    }
}

You can read more about it over here -- Really good article

Another option is to use MessagingCenter