Question: My Web Service returns xml.In OnInvoke method I have xml data it contains time and some text that are to be shown at given times on popup.

Answer: 
Normal message box access is as follows

```
MessageBox.Show("Enter your  data here");

```

But i am not sure about the message box access while the app is in ideal. 

But you can show a Toast message, while the app is in ideal also.

here the sample code to show a Toast message 

```
 Microsoft.Phone.Shell.ShellToast toast = new Microsoft.Phone.Shell.ShellToast();
            toast.Content = "mydata";
            toast.Title = "title";
            toast.NavigationUri = new Uri("/LocationDealsPage.xaml", UriKind.Relative);
            toast.Show();

```
You can make a message box according to your own design using user control. Then make an object of that control on your class where you want to use it. Make a popoup object and set control object as the child of pop up object.

```
UserControlName objectname = new UserControlName ();

PopUP popup = new PopUP();
popup.Child = objectname ;
popup.IsOpen = true;

```

I think it will help you.
<http://msdn.microsoft.com/en-us/library/system.windows.controls.primitives.popup.child(v=vs.95).aspx>

<http://www.geekchamp.com/tips/how-to-get-user-input-from-a-popup-in-windows-phone>