Best Practices for Self Updating Desktop Application in a network environment

Question

I have searched through google and SO for possible answers to this question, but can only find small bits of information scattered around the place, most of which appear to be p

Answer 1

From practical experience, don't forget to add functionality for updating the update engine. Which means that performing an update is usually a two step approach

1. Check if there are updates to the update engine
2. Check if there are updates to the actual application

Do you force an update if the clients software is out of date, but not going to break when trying to communicate with other version of the software or the database itself? If so how do you signify this breaking change?

A common practice is to have a "ProtocolVersion" method which indicates the lowest/oldest version allowed.

The "ProtocolVersion" can either supplied by the client or the server depending on the trust level you have between the client and the server. In a low trust level it is probably better to have the client provide the "ProtocolVersion" and then deny access server side until the client is updated. In a "high trust level" scenario it will be easier to have the server supply the "ProtocolVersion" it accepts, and then all the logic for adapting to this - including updating the client application - implemented in the client only. Giving the benefit that the version check/handling code only needs to be in one place.