private void SaveMapping()
        {
            var list    = SPContext.Current.Web.Lists[ListId];
            var mapping = Mapping ?? new ListMapping
            {
                Id        = Guid.NewGuid(),
                ListName  = list.ID.ToString(),
                TableName = ddlDbTables.SelectedValue,
                Key       = ddlTableKey.SelectedValue
            };

            // collect mapping info
            mapping.ListMappingFields.Clear();
            foreach (RepeaterItem rItm in ColumnsMapperRep.Items)
            {
                var dbColumnId   = ((HiddenField)rItm.FindControl("hidDbColumnId")).Value;
                var shpFieldName = ((DropDownList)rItm.FindControl("ddlListFields")).SelectedValue;

                if (!string.IsNullOrEmpty(shpFieldName))
                {
                    mapping.ListMappingFields.Add(new ListMappingField {
                        Id        = Guid.NewGuid(), ListMappingId = mapping.Id,
                        FieldName = dbColumnId,
                        ItemName  = shpFieldName
                    });
                }
            }
            if (mapping.ListMappingFields.IsEmpty())
            {
                throw new Exception("Select at least one mapping pare.");
            }
            // save mapping
            _configService.SaveMapping(mapping);

            // add EventReceiver
            AddReceiverToList(list, Constants.ReceiversNames.SYNC_DATA_ADDED, SPEventReceiverType.ItemAdded, 10010);
            AddReceiverToList(list, Constants.ReceiversNames.SYNC_DATA_UPDATED, SPEventReceiverType.ItemUpdated, 10011);
            AddReceiverToList(list, Constants.ReceiversNames.SYNC_DATA_DELETING, SPEventReceiverType.ItemDeleting, 10012);
        }