Infralution Support

[Guest]

Hi,

I'm trying to decide how best to use evaluation monitor in my product. I'd like to give users a 30 day trial, which I can do with Evaluation Monitor. But what happens if they decide not to buy, and then 6 months down the line download the next point release of my product?

From what I can tell, they'd get denied access to the product. For this reason, is it best to change the productId each point release, or somehow reset the evalution monitor on uninstall, or use some other trick with giving these people a special trial license?

Thanks.

[Rich]

Odd. I thought I'd logged in to the forum posting my question!

[Infralution]

Changing the product ID that you pass to the EvaluationMonitor when you release major new functionality may well be a good idea. That would allow customers a new evaluation period for the new point release.

An alternative is to provide a mechanism to extend or reset the evalution period by issuing a user with a special key. You can do this in one of two ways.

The simplest way to do this is to check for a special character sequence entered as the license key. If the user enters this then you call EvaluationMonitor.Reset to reset the evaluation monitor. Of course this isn't very secure because someon could decompile you app and reverse engineer it to determine the required character sequence. This isn't a major problem if your trial version has limited functionality anyway. And since you can never prevent a really clever user circumventing trial periods (by resetting information stored on their hard disk) it is a good idea not to rely only on the evaluation period.

The second means of doing this is more secure but perhaps a bit more work. In this case if a customers trial has expired you issue them with a license key that has some information in the ProductInfo that identifies it as an evaluation license (eg "E90") might mean an evaluation license for ninety days. When you read the license you check for this product info and if present you change the allowed evaluation period accordingly (but still display the licensing dialog).
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Infralution Support

[Rich]

Unless I misunderstand you, the first option of EvaluationMonitor.Reset sounds very open to abuse. Once a trial user has the code, they can keep entering it every 30 days, and hence circumventing the trial period completely.

I prefer your second option, with a maximum extension no longer than the time between releases.

Thanks. I'll get implementing...