如何禁用“ RadContextMenu”的焦点并将焦点重新设置为按钮“ aspxbuttonimage”？

Question

我有一个aspx代码：

<td valign="middle" nowrap>
    <telerik:RadContextMenu ID="lbtnPrint" runat="server" OnItemClick="lbtnPrint_Click" OnClientLoad="storeContextMenuReference">
        <items><telerik:RadButton RenderMode="Lightweight" EnableSplitButton="true" ID="SplitButton" AutoPostBack="false" runat="server" Text="<%$ Localization:export %>" OnClientClicked="OnClientClicked" OnClientLoad="storeSplitButtonReference">
                                            <icon primaryiconurl="~/images/print.gif" />
                                        </telerik:RadButton>  
            <telerik:RadMenuItem Value="word" ImageUrl="~/images/doc.png" Text="<%$ Localization:exportWord %>">
            </telerik:RadMenuItem>
            <telerik:RadMenuItem Value="excel"  ImageUrl="~/images/xls.png" Text="<%$ Localization:exportExcel %>">
            </telerik:RadMenuItem>
            <telerik:RadMenuItem Value="pdf"  ImageUrl="~/images/pdf.png" Text="<%$ Localization:exportPdf %>">
            </telerik:RadMenuItem>
        </items>
    </telerik:RadContextMenu>
</td>

<tr id="tr1" runat="server">
    <td colspan="2">
        <dx:aspxbuttonimage runat="server" id="lbtnRefresh" imagesrc="~/images/ARROW_EXPAND.gif" onclick="lbtnRefresh_Click" text="<%$ Localization:Apply %>" />
    </td>
</tr>

在上面的代码中，焦点设置为“ RadContextMenu”。因为，当我按下“ enter”键时，上下文菜单被下拉而不是单击按钮。如何通过按“输入”键使按钮可点击？