Programming C#, Third Edition

Shared Assemblies

You can create assemblies that can be shared by other applications. You might want to do this if you have written a generic control or a class that might be used by other developers. If you want to share your assembly, it must meet certain stringent requirements.

First, your assembly must have a strong name. Strong names are globally unique.

Tip

No one else can generate the same strong name as you, because an assembly generated with one private key is guaranteed to have a different name than any assembly generated with another private key.

Second, your shared assembly must be protected against newer versions trampling over it, and so it must have version control.

Finally, to share your assembly, place it in the Global Assembly Cache (GAC) (pronounced GACK). This is an area of the filesystem set aside by the CLR to hold shared assemblies.

The End of DLL Hell

Assemblies mark the end of DLL Hell. Remember this scenario: you install Application A on your machine, and it loads a number of DLLs into your Windows directory. It works great for months. You then install Application B on your machine, and suddenly, unexpectedly, Application A breaks. Application B is in no way related to Application A. So what happened? It turns out, you later learn, that Application B replaced a DLL that Application A needed, and suddenly Application A began to stagger about, blind and senseless.

When DLLs were invented, disk space was at a premium and reusing DLLs seemed like a good idea. ...