agregarle atributos a caja de texto de un gridview

  protected void gvReporteStock_RowDataBound(object sender, GridViewRowEventArgs e)
    {

        if (e.Row.RowType == DataControlRowType.DataRow)
        {

            (e.Row.FindControl("TextBox3") as TextBox).Attributes.Add("onkeydown", "soloNumeros();");
           
        }
    }