call dropdownlist selectedindexchanged event in gridview rowdatabound event

protected void gvMeatDispatch_RowDataBound(object sender, GridViewRowEventArgs e)
{
    try
    {
        DataTable dtpartyname = new DataTable();
        objRetailPL.status = 4;
        dtpartyname = objRetailBAL.GetType(objRetailPL);

        DropDownList ddlpn = (DropDownList)e.Row.FindControl("ddlpartyname");
        if (ddlpn != null)
        {
           // ddlpn.SelectedIndexChanged += new EventHandler(ddlbranchdate_SelectedIndexChanged);                

            ddlpn.Items.Add(new ListItem("--Select--", "0"));
            ddlpn.SelectedIndex = ddlpn.Items.Count - 1;
        }
    }
}