强类型的对象： Model.Categories category_model = e.Item.DataItem as Model.Categories;直接强转成该对象；
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
FamilyMemberTable member = e.Item.DataItem as FamilyMemberTable;
if (member != null)
{
HiddenField hidID = e.Item.FindControl("hidID") as HiddenField;
.......................
弱类型的DataTable： var rowData = e.Item.DataItem as DataRowView; 将item转成行视图DataRowView；
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
var rowData = e.Item.DataItem as DataRowView;
if (rowData != null)
{
#region ID
var hfUserID = e.Item.FindControl("hfMessageID") as HiddenField;
if (hfUserID != null)
{
hfUserID.Value = rowData["MessageID"].ToString(); //每一行用索引访问
}
.................