Add Style For Item In Datalist?

I had Datalist and I want to give item style when I click on it to show user the he select this item I did my code but when I selected item It didnot have any style

protected void DataList3_ItemDataBound(object sender, DataListItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
e.Item.Attributes["onmouseover"] = "this.style.cursor='hand';this.style.textDecoration='underline';";
e.Item.Attributes["onmouseout"] = "this.style.textDecoration='none';";
e.Item.Attributes["onclick"] = ClientScript.GetPostBackClientHyperlink(this.DataList3, "Select$" + e.Item.ItemIndex);
}