ListItemCollection myListItemCollection = new ListItemCollection();
// Creates an array of ListItems that are used to populate the collection.
System.Web.UI.WebControls.ListItem[] newListItemArray = new ListItem[tempDataTable.Count];
// Populates the array of ListItems with generic data.
for (int i=0; i < tempDataTable.Count; i++) {
newListItemArray[i] = new ListItem();
newListItemArray[i].Text = "Item " + i.ToString();
newListItemArray[i].Value = i.ToString();
}
// Adds an entire array of ListItem objects to the collection.
myListItemCollection.AddRange(newListItemArray);