Hi Karan,
Target Retrieve Dynamic is obsolete in CRM 2011, and functionality is replaced now.
You can retrieve any kind of entity either standard or custom in the single object called Entity.
E.g
Entity new_customentity = Service.Retrieve("name","GUID","columnset");
Hope it helps.
Thanks and regards,
Hiren Solanki.
Please vote or mark as a answer if it helped you.