问题
For a handled exception in Visual Studio 2013 I could view the exception dialog in a catch block by clicking the red exception helper icon. In Visual Studio 2015 this is missing. The dialog still shows when the exception is thrown, so that is not the issue. Though there is a workaround in this answer, this doesn't provide the functionality of the exception dialog (e.g. copy to clipboard).
回答1:
Apparently it's no longer there, so you have to watch $exception, which always has the current exception object.
According to this, I'd try enabling/disabling Tools | Options > Debugging | General | Use the new Exception Helper, or trying the update mentioned in this message, posted on Dec 5th 2017:
This issue has been fixed and is now available in our latest update. You can download the update via the in-product notification or from here: https://www.visualstudio.com/vs/
来源：https://stackoverflow.com/questions/47872167/where-did-the-exception-assistant-go-for-visual-studio-2015