Changing a .net Framework dll requires re-signing?

Question

If we decompiled a .net framework dll (eg .System.Linq.Expressions.dll ) present in GAC, made some changes in IL and assembled it back do we need to re-sign it ?

Answer 1

To be able to add an assembly to the GAC you need to sign it with a strong name. And you will not be able to sign it as Microsoft because you do not have their private key. This means that the recompiled assembly gets a new strong name which is different from the strong name of the original assembly.

Answer 2

Yes.

One of the ideas behind signing an assembly is to prevent someone from tampering with it.

So, if you do change the assembly, it'll need to be re-signed.