Hi Dave,

I've done some further research and I think I've found the root cause now.

Per the documentation of LoadFile:

<quote>
Use the LoadFile method to load and examine assemblies that have the same
identity, but are located in different paths. LoadFile does not load files
into the LoadFrom context, and does not resolve dependencies using the load
path, as the LoadFrom method does. LoadFile is useful in this limited
scenario because LoadFrom cannot be used to load assemblies that have the
same identities but different paths; it will load only the first such
assembly.
</quote>

Two points here:

1) LoadFile does not resolve dependencies using the load path.

Therefore, if we call LoadFile("<path>\ClassLibrary2.dll") which references
ClassLibrary1.dll, it will not use the path of ClassLibrary2.dll to load
ClassLibrary1.dll. Instead, it will look in current AppDomain's loaded
assemblies list first, it not found, then it will try to load from GAC.
(This is why I found previously that adding your WindwardReports.dll to GAC
will succeed)

2) LoadFile does not load files into the LoadFrom context.

This means assembly loaded with LoadFile cannot be used by furthre LoadFile
calls. In other words, if we call LoadFile("<path>\ClassLibrary1.dll")
first, then call LoadFile("<path>\ClassLibrary2.dll"), it still cannot find
ClassLibrary1.dll since it's not loaded into the context. However, if we
"Add Reference" to ClassLibrary1.dll first in the main application, then
further call to LoadFile("<path>\ClassLibrary2.dll") will succeed since the
assembly is already in the context. (This is why my test project fail to
reproduce the issue on the very beginning: since you mentioned that the
add-in is using the shared assembly, so my test project added a reference
to ClassLibrary1.dll in the main application.)

Therefore, the fix to your issue is to use LoadFrom instead of LoadFile.
However, LoadFrom will only load an assembly if it's not already loaded.
Following code will demostrate the point:

Assembly ass1 =
Assembly.LoadFrom(@"c:\test\ClassLibrary1\bin\x86\Debug\ClassLibrary1.dll");
Console.WriteLine(ass1.CodeBase);
Assembly ass2 =
Assembly.LoadFrom(@"c:\test\ClassLibrary2\bin\x86\Debug\ClassLibrary1.dll");
Console.WriteLine(ass2.CodeBase);

Above code will both print out
"c:\test\ClassLibrary1\bin\x86\debug\ClassLibrary1.dll", second call to
LoadFrom will not load it again from a second place. This is the case
"assemblies that have the same identities but with different paths".

Hope this helps.

Regards,
Walter Wang (wawang@online.microsoft.com, remove 'online.')
Microsoft Online Community Support

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