When would I register a crm 2011 online plugin for pre-validation stage?

Question

I understand that a plugin registered for pre-validation executes outside of the database transaction but I'm not sure I can think of a scenario when this would be preferable to pre-operation. Can someone give me an example of where pre-validation registration might be useful?

Answer 1

We have a few plugins registered on the 'PreValidation' event although this is on premise, not online.

I did not write these specific plugins myself but I can describe one and give the justification for using 'PreValidation' rather than 'PreOperation'.

Entity: Account

Event: Delete

Logic: Plugin runs pre validation. Checks that there are no contacts referencing any of the account's addresses. If any are found, stop execution. If not, delete account.

e.g.

Account 'Stackoverflow' has address 'Jeff Attwood's House' and Contact 'glosrob'. 'glosrob' is referencing 'Jeff Attwood's House' through a customisation. If a user selects to delete 'StackOverflow', we should detect 'glosrob' is referencing an address and prevent the delete.

The reasoning behind this was the developer found that at the PreOperation stage, some aspects of the delete had already happened, namely the cascade deletes. The logic of the plugin requires us to check all contacts - by registering at PreOperation, contacts under the account had already been deleted, rendering the check obsolete.

In our previous scenario, when the user selected to delete 'StackOverflow' Account, the Contact 'glosrob' would be deleted before the plugin runs. Therefore when the plugin did run afterwards, it would allow the delete.

As with most things in CRM, it all comes down to requirements and solutions, but I think that gives you an idea of why/when you might use a PreValidation stage. We have a few others with similar reasoning that run on the 'Delete' event.

Answer 2

I know its very old post, came here while digging for an answer for the same question... Later I found one key point from MSDN on the same topic and i thought it would be helpful If I post the infromation over here for all..

The Prevalidation plugin would happen prior to the security checks. For ex: If an account is "VIP" account and you dont want this account record to be deleted (no matter even he is a super user/admin), then this better can happen in pre validation. Because at that time you are not really bothered about who the user is and what sort of permissions he has (even he may not have any permissions to delete any records in the system), CRM will go and check the database for the user's security roles during the pre operation and that is where the first database hit would happen.. before that it self, we can stop the exucution of the plugin based on our validation rules..

I hope that make sense...

Thank you

Regards Srikanth