Compare Activity Party List Users

Hi All,

Today i have a Scinario that i need to Compare Pre and Post Image of party List and i need to add the users in Access Teams..

My Scinario is :

--> On update of requiredattendees i need to check weather any new Users Added or not. If Added i need to Add them in Access Team.

      --> On Update of requiredattendees i need to check any Existing users removed or not. If removed i need to remove them from Access Team.

For Achieving below Scinario i need to Use Pre and Post Image. Can Any one Guide me to achieve this in c# Plugins.

 EntityCollection PostRecipients = postImageEntity.GetAttributeValue<EntityCollection>("requiredattendees");
 EntityCollection PreRecipients = preImageEntity.GetAttributeValue<EntityCollection>("requiredattendees"); 

for (int j = 0; j < PostRecipients.Entities.Count; j++)
{
ActivityParty PostAP = PostRecipients[j].ToEntity<ActivityParty>();                                
}
for (int j = 0; j < PreRecipients.Entities.Count; j++)
{
ActivityParty PreAP = PreRecipients[j].ToEntity<ActivityParty>();
}

I need to Compare PostAP and PreAP and i need to get Value as which user Added and which User Removed.