What does Visual Studio use to determine when to uninstall SharePoint Add-in?

Question

I have two SharePoint apps that behave differently in Visual Studio 2017 when I run it on the SharePoint hosted server.

For one app, I can make changes in the Default.aspx file and associated JavaScript files and when I click on Start, it always skips the uninstall step because the SharePoint Add-in on the server is already current.

For another app, Visual Studio always uninstalls the SharePoint Add-in even if nothing changed in the app. I click 'Start', loaded the app, clicked 'Stop' and 'Start' again. Visual Studio went ahead and uninstalled the app.

I compared the Project Settings between both apps and they were the same.

Does anybody know where else I can look to find out why the apps are treated differently in Visual Studio?

Thanks in advance

Update I noticed that when I build the app that keeps getting uninstalled, I see this in the build output... ------ Build started: Project: myapp, Configuration: Debug Any CPU ------ Successfully created package at: C:\Users\Eric\Documents\code\myapp\bin\Debug\myapp.debugapp

I don't see this in the app that skips the uninstall step. Maybe this could be the issue.

Answer 1

It turns out that the 'Target SharePoint Version' settings under Properties -> SharePoint were different between the two.

The app that kept uninstalling was set to SharePoint 2013 while the one that did not keep uninstalling was SharePoint Online. Once I changed the problematic app to SharePoint Online, I was able to avoid having the app get uninstalled.