Making Local Assemblies of different versions Coexist

[Mart Rogers]

We have a situation where we have decided (in an attempt to keep things
simple) to stick to local assemblies rather than global ones.
However we now have the following situation looming

AssyA depends on AssyB depends on AssyD version 1
AssyA depends on AssyC depends on AssyD version 2

Obviously we cannot copy both versions of AssyD to the AssyA's bin
directory. Is the only sensible way around this (rather than going the GAC
route) to name the Assemblies by version number (e.g. AssyD001 andAssyD002).

How much of a development pain is the GAC route - all that key generation
stuff seems overkill for our 'local' libraries.

Many Thanks.

 

[SR]

Hi
I dont think that u need to rename the assemblies. In
fact if i remember right, if the name of an assembly is
changed after it was compiled, then it will throw an
exception.

Do note that ".Net by default looks for the same version
of the assembly even if a new version is available. So i
think if u use the structure properly you can achieve
this."

so you can achieve what you want by

Build the AssemblyB with Version X of AssemblyD
Build the AssemblyC with Version Y of AssemblyD


1)Place the different versions of Assembly D in the
different subdirectories of the bin folder with the
version name as the sub-directory name.

2) Then use the CodeBase Element in the Config file to
specify the File Path for each version of Assembly D

When ur app is run, Assembly B will search with Version X
of AssemblyD( coz that was how it was built) and the code
base will ensure that it gets the version X

As Assembly C was built with Version Y of Assembly D,
this Version Y will be searched and again code base will
ensure that the correct version is got


Check out the links

General Notes on Assembly Location :
http://msdn.microsoft.com/library/default.asp?
url=/library/en-
us/cpguide/html/cpconhowruntimelocatesassemblies.asp

Locating the Assembly through Codebases :
http://msdn.microsoft.com/library/default.asp?
url=/library/en-
us/cpguide/html/cpconstep4locatingassemblythroughcodebaseso
rprobing.asp

How to Specify Code Base :
http://msdn.microsoft.com/library/default.asp?
url=/library/en-us/cpgenref/html/gngrfcodebase.asp


regards,

sr

 

[Suzanne Cook [MS]]

The version is always checked if both (a) the assembly reference included
the version and (b) the assembly is strongly named. It doesn't matter for
that whether the assembly is in the GAC or elsewhere.

If you intend to only change the version number, and not the rest of the
assembly identity, you need to strongly name it or else use something
besides just the Load context. Otherwise, the version is not part of the
assembly identity, and you'll only get one version loaded and used by both
AssemblyB and AssemblyC.

Plus, as you noticed, compiling against two versions of the same assembly
isn't supported by compilers that I know of yet.

So, my #1 recommendation is to take a hard look at your app and try to make
it use only one version of AssemblyD. Then, have just that one copy in the
ApplicationBase. If that's just not possible, you may want to consider
changing the assembly identity (the simple name or culture for non-strongly
named assemblies, or the simple name/version/public key token/culture for
strongly named assemblies).

Suzanne Cook
My .NET CLR Loader blog: http://blogs.gotdotnet.com/suzcook/

 

[Mart Rogers]

The version is always checked if both (a) the assembly reference included
the version and (b) the assembly is strongly named. It doesn't matter for
that whether the assembly is in the GAC or elsewhere.

Thanks - my confusion arose because I understood that if an assembly stores
the version of its references in its manifest then it can use this version
info to determine what to load. This is not true. It appears that all
referencing assemblies do seem to store this version info in their manifest
(even weakly named ones) but it just does not get used unless the whole of
the strong name is present.