Append code to a function in C#

In my project, I am used a lot of classes and methods. Project is working fine. But now I need a performance optimization. I want a logging option for track execution time of each method. Changing each function code is not good.

So my question is, is there any option for append/inject some code block to every method, without touch the existing code; I need a log entry before and after execution of a method with time.

I am not prefer a third party tool.

Thanks in advance..