仅在有附件时显示加载项命令按钮

Question

我尝试使加载项命令按钮仅在有附件时可见。有可能吗？

我希望我可以将“规则”节点添加到“控制”节点，但无法完成：

<Control xsi:type="Button" id="hButton2">
    <Label resid="hButton2Label" />
    <Supertip>
        <Title resid="hButton2SupertipT" />
        <Description resid="hButton2SupertipD" />
    </Supertip>
    <Icon>
        <bt:Image size="16" resid="h-button2-icon-16" />
        <bt:Image size="32" resid="h-button2-icon-32" />
        <bt:Image size="80" resid="h-button2-icon-80" />
    </Icon>
    <Action xsi:type="ShowTaskpane">
        <SourceLocation resid="hSourceLocation2"/>
    </Action>
    <Rule xsi:type="ItemHasAttachment" /> <-------------------- won't work
</Control>

Answer 1

Rule 元素仅适用于 CustomPane 扩展点，不能在 Control 元素中定义：https://dev.office.com/docs/add-ins/outlook/manifests/define-add-in-commands。另见：https://dev.office.com/docs/add-ins/outlook/manifests/activation-rules