Trigger N:N Association event and Dassiciation event in CRM Plugin

-- ===================================================================================================
-- Enable Associate and Disassociate Plug-in Events
-- execute the following query to CRM database, it will add two entries in SdkMessageFilterBase
-- 'DisassociateEntities' and 'AssociateEntities' from SdkMessageBase which is not listed
-- --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
USE CrmDev_MSCRM
GO

-- Find the deployments SDK Filter ID for the
-- Associate and Disassociate Entity SDK Messages
DECLARE @DisassociateEntitiesFilterId uniqueidentifier
DECLARE @AssociateEntitiesFilterId uniqueidentifier
SET @DisassociateEntitiesFilterId = (SELECT SdkMessageId FROM SdkMessageBase WHERE [Name] = 'DisassociateEntities')
SET @AssociateEntitiesFilterId = (SELECT SdkMessageId FROM SdkMessageBase WHERE [Name] = 'AssociateEntities')

-- Enable the Associate and Disassociate Filters to be valid for custom processing
-- Custom Processing means "you register plug-ins against it"
-- Note: We only do this for the "generic" (OTC == 0) case, just to be safer
UPDATE SdkMessageFilterBase SET IsCustomProcessingStepAllowed = 1 WHERE SdkMessageId = @DisassociateEntitiesFilterId AND PrimaryObjectTypeCode = 0
UPDATE SdkMessageFilterBase SET IsCustomProcessingStepAllowed = 1 WHERE SdkMessageId = @AssociateEntitiesFilterId AND PrimaryObjectTypeCode = 0
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
The above query will enable the 'DisassociateEntities' and 'AssociateEntities' message in the plug-in registration tool. While registering the plug-in select the entity name as ‘none’

While executing the plug-in you will be getting four parameter as input parameters from the plug in context along with the other properties :

1. Related Entity1 GUID and entity name
2. Related Entity2 GUID and entity name
3. Relation hsip name (nothing but intersect hidden N:N entity name)
4. Optional parameter.

Using these value you can implement you logic.

Sample Code for N:N relationship with a custom entity and System User:

public void Execute(IPluginExecutionContext context)
{
try
{
crmservice = context.CreateCrmService(true);

if (context.MessageName == "AssociateEntities")
{

if (context.InputParameters.Properties["RelationshipName"].ToString() == "new_new_customentity_systemuser")
{
string oId = string.Empty;
string SharedUserId = string.Empty;

oId = (context.InputParameters.Properties["Moniker1"] as Moniker).Id.ToString();

SharedUserId = (context.InputParameters.Properties["Moniker2"] as Moniker).Id.ToString();

// write you logic here

}
}

}
catch (System.Web.Services.Protocols.SoapException ex)
{
LogWriter.LogInfo(ex.ToString());
}

catch (Exception ex)
{
LogWriter.LogInfo(ex.ToString());
}
}

Note : As we have defined 'none' as the entity name while registering the plug-in, so this plug-in will get triggered when ever user will do add existing or remove existing, for any entity. So while writing the logic relationship name is required to identify from where plug-in has been triggered.

References: http://consulting.ascentium.com/blog/crm/Post533.aspx
http://mscrm-chandan.blogspot.com/2010/03/trigger-nn-association-event-and.html