After tracing I finally found why the application is so slow. It really used too much time to open a database connection for logging, actually is existed.
This function is wrapped in an dll. Although connection.open failed, it doesn't throw the exception, that remind me, do NOT write such code, which make other develper confused.
Tools is dotTrace3.1, very powerful.
转载于:https://www.cnblogs.com/beyondjay/archive/2008/12/25/1362343.html