crm cascade delete does not fire plugin

Question

In crm i have solution with several entities. There are three that are causing a problem. Lets call them A, B and C.

A and B have a one to many relation with a cascading effect on deletion

B and C have a one to many relation without a cascading delete.

for B i have developed a crm plugin that, when deleted, it removes C as well. A sort of cascading delete plugin. I cannot create a cascading between B and C, since C is already in a cascading relationship with another entity.

When i delete any entity B, it fires off plugin code and deletes all children of C. When i delete any entity A, it cascade deletes B, but it does not fire off the plugin.

How can i ensure that the plugin does fire, without creating a plugin for entity A? I am fairly new at crm so i don't really know where to look for this kind of problem.

UPDATE

The plugin used to fire at the 'Pre-validation' stage. Changing it to 'Pre-operation' actually caused the plugin to fire. Unfortunately at this stage all Child references of the object where already removed. So now when A is deleted B is cascade deleted, and the plugin fires, but i cannot find any of it's child entity C references

Answer 1

Create an object which will store the child references and pass it into the "Shared Variables" in the Pre-Validation stage. Then you can access the shared variables in the pre-operation stage: https://msdn.microsoft.com/en-us/library/gg328579.aspx. You will need plugins registered at both steps, but this will handle both of your challenges.

Answer 2

Register your plugin on the pre-operation stage of the delete message of entity B. Then register a pre-image for the entity to get the original lookup fields to entity C.

Answer 3

During cascade delete, only the triggering entity's PreValidation will be called. For your entity B this means that this stage will be skipped.

As Joseph noted, setting a shared variable in PreValidation can generally be used to have information about already deleted data available in PreOperation, but you would have to ensure that this shared variable is set also when deleting A.

In case any of your entities are solution aware, deleting the solution with these records will also trigger a cascade delete, whereby PreValidation is only called on the solution entity.

Henk's suggestion is feasible, if the set of C records related to B do not need any kind of processing, like sorting.