返回Windows Phone时，将数据传回上一页的最佳方法

Question

What would be the best approach to pass data back to the previous page when I click the back button in Windows Phone. What I want to do is, when the user goes back to the main page from one of my child pages, if I saved something in the child page, the main page should refresh de data. When I go forward is simple, I simply use the QueryStringm, but I don't know how to do when I go back. I tried this:

private void PhoneApplicationPage_BackKeyPress(object sender, System.ComponentModel.CancelEventArgs e)
{
    e.Cancel = true;
    NavigationContext.QueryString.Add("test", "test");
}

and then, in the main page I tried to do this:

protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
    if (e.NavigationMode == System.Windows.Navigation.NavigationMode.Back)
    {
        if (NavigationContext.QueryString.ContainsKey("test"))
        {
            MessageBox.Show(NavigationContext.QueryString["test"]);
        }
    }
}

I did this just for testing purposes, but I had no luck, I've searched the internet for an answer but I didn't find any satisfying one. I thought about putting in the App.xaml.cs a dictionary called Pending, where I would hold data that should be handled at certain points, and then, if I went back to the main page and I had the data in this dictionary I would refresh the ui. Would it be a good idea??

Thank you all!

Answer 1

What I would recommend is if you are following the MVVM architecture, set a property in the view model from child page and access it on the parent page. I hope it helps you