public void ManageLists(XrmServiceContext context, Contact contact) { foreach (RepeaterItem item in MarketingList.Items) { if (item != null) { RepeaterItem repeaterItem = item; var ml = context.ListSet.First(m => m.ListId == new Guid(((HiddenField)(repeaterItem.FindControl("ListID"))).Value)); var listCheckBox = (CheckBox)item.FindControl("ListCheckbox"); var contactLists = contact.listcontact_association.ToList(); var inList = contactLists.Any(list => list.ListId == ml.ListId); if (listCheckBox.Checked && !inList) { context.AddMemberList(ml.ListId.Value, contact.ContactId.Value); } else if (!listCheckBox.Checked && inList) { context.RemoveMemberList(ml.ListId.Value, contact.ContactId.Value); } } } }