What are Side-by-side Assemblies?

Question

I came across Side-by-side Assemblies for the first time today while trying to install a Debug install set to a test machine. I managed it in the end, but was left with several questions:

1. Whare are Side-by-side assemblies?
2. How does Windows deal with these assemblies differently from other assemblies
3. How do applications depending on Side-by-side assemblies deal with these differently from normal assemblies
4. Under what situations might someone want to create a Side-by-side assembly?

Answer 1

A starting point for understanding side-by-side assemblies and what they're for would probably be the "Isolated Applications and Side-by-Side Assemblies" reference on MSDN.

Essentially, side-by-side assemblies are a way to ensure that a given application will always use a specific version of a DLL, particularly Windows system DLLs (such as the Common Controls), no matter the Service Packs, Updates or new applications installed after it.

Other links of interest:

• MSDN: Side-by-side assemblies (windows)
• Wikipedia: Side-by-side Assembly