How to set Grid view column width for dynamic data

protected void Gridname_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            Gridname.Columns[1].ItemStyle.Width = 10;
            Gridname.Columns[2].ItemStyle.Width = 40;
        }
    }

Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index