Why I can't debug Add-in in Visual Studio.NET?

Hello folks,

I am new to add-in, I am now stucked by the debugging.

My VS.NET is newly installed. I created a new add-in using the template, I added only one line to this add-in, simply pop up a message saying it's running.

The add-in will show up in normal mode. However, when I try to debug it, it is not showing up in the debug environment. I check the add-in manager(in debug env), it's there.

I tried the following methods I digged from Internet:
1. Click on the .reg file to re-register the add-in.
2. Run devenv /setup in Command Prompt mode.

But it just disappeared.

What the heck problem it is?

Thanks. Any hint will be appreciated.