c# - Time-based trial for an application - how to check when app was downloaded -


is there way access time app downloaded (or first launched, etc) of great in implementing trial run feature on app.

i don't remember how stand on win8 platform, winphone7.0/7.5 there's clear warning/guideline in official documents microsoft, saying:

do not rely on usage time limited trials protect app’s value.

typically, best protect value of full mode app limiting trial access key code paths. user may uninstall , retry app without restriction trial design offers full mode behavior limited time provides inconvenience barrier reuse.

source: creating trial apps windows phone

the problem in time-based trials simple: when uninstall application, phone's operating system will erase completely. means, nothing left, not byte. if write data isostorage, purged upon deletion.

so, if make time-base trial , store "installed date", user uninstall application , install again, , happy next free-trial period. if ok you, well, aware of that.

to make true time-trial you'd need create internet service application register phone's/user's uuid, , app need check @ service determine whether trial has passed or have been used previous installation..

what's more, microsoft phone appp guidelines state should not create application "turns off of features" @ point of time. irritates end-users , makes whole phone/platform "bad" user's point of view, because people don't lose once had.

iirc, @ point of time microsoft advised create two separate applications: 1 free , without features @ all, , 1 paid features. later, trialmodes included in market's workflow , microsoft's app licensing api introduced easy way determine if app works in "free trial" or "fully paid" mode, depending on whether downloaded market free or not.

i don't know 1 most-recent, let me paste three:

xna: http://msdn.microsoft.com/en-us/library/dd282459(v=xnagamestudio.30).aspx

sl: http://msdn.microsoft.com/en-us/library/windowsphone/develop/microsoft.phone.marketplace.licenseinformation.istrial

w8: http://msdn.microsoft.com/en-us/library/windows/apps/windows.applicationmodel.store.licenseinformation.istrial


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