Information Technology Reference
In-Depth Information
Side-by-Side Execution in the GAC
After an assembly is deployed to the GAC, it can be used by other assemblies in the system.
Remember, however, that an assembly's identity consists of all four parts of the fully qualified
name. So, if the version number of a library changes, or if it has a different public key, these dif-
ferences specify different assemblies.
The result is that there can be many different assemblies in the GAC that have the same
filename. Although they have the same filename, they are different assemblies and coexist per-
fectly fine together in the GAC. This makes it easy for different applications to use different
versions of the same DLL at the same time, since they are different assemblies with different
identities. This is called side-by-side execution .
Figure 10-16 illustrates four different DLLs in the GAC that all have the same filename—
MyLibrary.dll . Looking at the figure, you can see that the first three come from the same com-
pany, because they have the same public key, and the fourth comes from a different source,
since it has a different public key. These versions differ as follows:
￿
An English version 1.0.0.0, from company A
￿
An English version 2.0.0.0, from company A
￿
A German version 1.0.0.0, from company A
￿
An English version 1.0.0.0, from company B
Figure 10-16. Four different side-by-side DLLs in the GAC
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