As the matter of fact There is no tool which will give you 100% working source code, It's just like using Google Translator Korean To English and vice versa.
Making a working source code from binary requires a skill set of writing codes, understanding the behavior of application you trying to decompile (I would assume you've lost the source code and have exe file and trying to recover, don't do that to a property of someone without permission :) )
anyway you can try Dot Peek, .NET Reflector, IDA pro..
In your case you were not able to see the code in some methods so I would suggest you to take some time learning hooking the process finding the required offsets from the memory and check it's behavior, you can either disassemble those chunks of methods or just reproduce the functionality of those methods how it behaves ( that requires certain amount of skills in reverse engineering )
Hope I was able to deliver the concept as per my knowledge tried to keep it simple.