How to handle prod and dev connection

i setup db connection in web.config now, before i move code from dev server to prod server...i need open web.config and change Data Source and put prod db server name.
this is risky...i can forget it and do test in prod in future. How to avoid this?
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what is best way to handle dev connection and production connection in same application?
<add name="conprod" connectionString="Persist Security Info=False; Data Source=; Initial Catalog=; User ID=; Password=; Application Name=" providerName="System.Data.SqlClient"/> 
<add name="condev" connectionString="Persist Security Info=False; Data Source=; Initial Catalog=; User ID=; Password=; Application Name=" providerName="System.Data.SqlClient"/>

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by doing this i know, which ...