How to preserved Application Setting for new upgrade?

When upgrading my old app, how do I preserved those old Application Setting that had been set by previous app, so that 开发者_高级运维the new app can use back the old app setting?

thanks.

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Here is a MSDN article on ClickOnce Application Settings which explains the approach taken by ClickOnce for migrating application and user settings when upgrading to a newer version of the the application.