How do I implement base view functionality on Windows Phone 7?

Lets say t开发者_如何学Pythonhat on all my views, or generally at any time in my app, I want to be able to show an error message popup, and it always looks the same. How do I do that?

First thought is having all my view models extend a base view model which facilitates these things, but after that, do I have this base view model actually create the UI widgets and display them?

thanks, Mark

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If you've got some common functionality that you want to provide across a range of views, then you can implement a base class that inherits from the PhoneApplicationPage, and then derive all your classes from that class instead. The XAML for your pages then looks like this:

<local:BasePage xmlns ...
                xmlns:local="clr-namespace:MyNamespace"
                x:Class="MyNamespace.MyPage">

However, you will not be able to define common UI components in the XAML for your base page. If you wanted to have common UI components you would have create them manually in the code-behind for the base page, perhaps in a handler for the Loaded event, but I think a better solution would be to provide your common UI in a UserControl, which you then add to each of your pages.

If you want to show a Toast or Message Box, then I would recommend the ToastRequestTrigger and MessageBoxRequestTrigger from the Silverlight Toolkit as described in the patterns & practices WP7 Developer Guide.

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you could probably define an event on base view model, which is fired inside view model whenever an error occurs, then in view, you can subscribe to this event and display the popup. You can carry error context in EventArgs of the fired event.

Additionally you could unify the logic for displaying the popup but that's probably another story :)

This is testable and nicely decoupled from the view.

Hope this helps, Robert