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Source Code

The SharedCarLibClient application can be found under the Chapter 15 subdirectory.

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Configuring Shared Assemblies

Like a private assembly, shared assemblies can be configured using a client *.config file. Of course,

because shared assemblies are deployed to a well-known location (the GAC), you will not use the

 element as you did for private assemblies (although if the client is using both shared

and private assemblies, the 
 element may still exist in the *.config file).

You can use application configuration files in conjunction with shared assemblies whenever

you wish to instruct the CLR to bind to a 

different version of a specific assembly, effectively bypass-

ing the value recorded in the client’s manifest. This can be useful for a number of reasons. For

example, imagine that you have shipped version 1.0.0.0 of an assembly and discover a major bug

some time after the fact. One corrective action would be to rebuild the client application to refer-

ence the correct version of the bug-free assembly (say, 1.1.0.0) and redistribute the updated client

and new library to each and every target machine.

Another option is to ship the new code library and a *.config file that automatically instructs

the runtime to bind to the new (bug-free) version. As long as the new version has been installed into

the GAC, the original client runs without recompilation, redistribution, or fear of having to update

your resume.

Here’s another example: you have shipped the first version of a bug-free assembly (1.0.0.0), and

after a month or two, you add new functionality to the assembly in question to yield version 2.0.0.0.

Obviously, existing client applications that were compiled against version 1.0.0.0 have no clue about

these new types, given that their code base makes no reference to them.

New client applications, however, wish to make reference to the new functionality found in

version 2.0.0.0. Under .NET, you are free to ship version 2.0.0.0 to the target machines, and have ver-

sion 2.0.0.0 run alongside the older version 1.0.0.0. If necessary, existing clients can be dynamically

redirected to load version 2.0.0.0 (to gain access to the implementation refinements), using an

application configuration file without needing to recompile and redeploy the client application.