How To Check Dll working or not

hi all,

I am software Engineer.We developed one application Which will get data and send data to server through http request.Some times it is working fine.Some times due to corruption of dlls it is not working properly.I collected what are the system dlls required to run my application.So What I want is know is how to check wether particular DLL in the system is working or not.Please help me.My Project is going to be live.