We have installed Visual Studio 2015 Community Edition on several Computer on my company. And now , as we are going to work on closed-source projects :
In short, is it possible to switch without reinstall all my 10 PC ? Best regards.
It is not possible to just enter the VS Professional license key, but you don't have to necessarily uninstall the Community version. However, you will have to run the VS Professional installer that will upgrade the Community version to the Professional one. This is also suggested here [1].
You will find here [2] an answer to a similar question, stating that although running the installer will upgrade the existing Community edition, uninstalling and reinstalling is recommended.
[1] https://social.msdn.microsoft.com/Forums/vstudio/en-US/6202c332-bf73-4073-8ee6-70a3c5402467/upgrading-from-community-to-professional-seems-impossible-how?forum=vssetup [2] Can Visual Studio Community 2015 be easily updated to Visual Studio Professional 2015