existing .dll file chnages possible???how?? in c#

Hey. You need to use decompiler which will read all files and that will show you what is inside those dlls. I used once jetbrains. There are so many others also exists. You can follow up with this link and can use anyone, https://stackoverflow.com/questions/18050615/how-to-open-dll-files-to-see-what-is-written-inside