public void ManageLists(OrganizationServiceContext context, Entity contact)
        {
            foreach (var item in MarketingListsListView.Items)
            {
                if (item == null)
                {
                    continue;
                }

                var listViewItem = item;

                var hiddenListId = (HiddenField)listViewItem.FindControl("ListID");

                if (hiddenListId == null)
                {
                    continue;
                }

                var listId = new Guid(hiddenListId.Value);

                var ml = context.RetrieveSingle("list",
                                                FetchAttribute.All,
                                                new Condition("listid", ConditionOperator.Equal, listId));

                var listCheckBox = (CheckBox)item.FindControl("ListCheckbox");

                if (listCheckBox == null)
                {
                    continue;
                }

                var contactLists = contact.GetRelatedEntities(XrmContext, new Relationship("listcontact_association")).ToList();

                var inList = contactLists.Any(list => list.GetAttributeValue <Guid>("listid") == ml.Id);

                if (listCheckBox.Checked && !inList)
                {
                    context.AddMemberList(ml.GetAttributeValue <Guid>("listid"), contact.GetAttributeValue <Guid>("contactid"));
                }
                else if (!listCheckBox.Checked && inList)
                {
                    context.RemoveMemberList(ml.GetAttributeValue <Guid>("listid"), contact.GetAttributeValue <Guid>("contactid"));
                }
            }
        }