vb.net arcgis add in, log4net does not work by installing esriAddIn

Hi everybody,

I want to use log4net in my vb.net for ArcGIS add-in. After I build the solution, it generates a .exe file and a .esriAddIn file.
The problem is when I run the .exe file (without open ArcMap), the log4net works, but when I install the .esriAddIn in ArcMap, and call a form from ArcMap, the log4net doesn't work at all.

I check from internet but most of the answers are talking about c#.net, this problem call me crazy, anybody has the experience of using log4net in vb.net ArcGIS add in?

Any help will be appreciated. thanks.