You need to set DisplayMode
has Hyperlink
(BulletedListDisplayMode.HyperLink
)
ImageItem.DisplayMode = BulletedListDisplayMode.HyperLink;
foreach (DataRow dr in dt.Rows)
{
ListItem li = new ListItem("PLACE-THE-LINK-TEXT", string.Format("../stream.aspx?type=={0}",dr["type"]));
//here how to add the `hl` to `li`
ImageItem.Items.Add(li);
}