private void Datagrid1_ItemDataBound(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
{
if (e.Item.ItemIndex>=0)
{ int index =e.Item.ItemIndex+1; e.Item.Cells[0].Attributes.Add("onclick","ChangeCellsStyle("+index+")");
}
}
<script language="javascript">
function ChangeCellsStyle(index)
{
var oTbl = document.getElementById("Datagrid1");
var tr1 = oTbl.rows.item(parseInt(index));
tr1.style.display=none;
}