在gridview中选择组样式

<asp:GridView ID="GridView1" runat="server" DataSourceID="SqlDataSource1" AutoGenerateColumns="False" DataKeyNames="CategoryID">
   <Columns>
        <asp:BoundField DataField="CategoryID" HeaderText="CategoryID" InsertVisible="False" ReadOnly="True" SortExpression="CategoryID" />
        <asp:BoundField DataField="CategoryName" HeaderText="CategoryName" SortExpression="CategoryName" />
        <asp:BoundField DataField="Description" HeaderText="Description" SortExpression="Description" />
    </Columns>
   <GroupStyle>
        <asp:GroupStyle HeaderText="CategoryName" />
    </GroupStyle>
</asp:GridView>