解决此问题的最干净的方法可能是推迟订阅ValueChanged事件，直到设置了最小基本范围为止.

Maybe the cleanest way to address this is to hold off subscribing to the ValueChanged event until after the Minimum baserange is set.

或者在尝试使用DataContext之前对其进行测试.

Or test DataContext before trying to use it.

-马克