向一个asp:复选框控件添加自定义属性

I am trying to add a custom data-required attribute to an asp Checkbox control, it works fine for all other controls I've used it on, but on checkboxs it renders the checkbox inside a span that has the custom attribute on. I've tried adding the attribute in the markup and tried adding it to the control in the code behind. Any ideas?I am trying to add a custom data-required attri