As Dave has said, there is nowhere near enough information here for us to begin to help you - we have no idea what you are trying to do, or where you are starting from. Remember that we can't see your screen, access your HDD, or read your mind - we only get exactly what you type to work with.
Suppose I phone you and ask you for help because my car has broken down - but don't tell you where I am, or what car I have, or what happened to it when it broke. How are you going to help me? You can't even come out to give me a lift without further information like where the heck I am!
So we don't even have any idea what your code looks like, what you have tried in order to fix it, or even what log4net.dll was "showing error" which made you remove it. We don't really have any idea what help you might need - and that's kinda important, don't you think?
Start here: Asking questions is a skill
] and think about what we need to know, and what you need to tell us in order to get help.
That doesn't just apply here: this is a real world problem, and a real world skill you need to develop!