Debugging "Could not load file or assembly" that only happens on some computers

Question

So I recently updated my software and with the new version I supply a new dll-file, lets call it My.dll. Now, the old version works just fine on every computer I have tried.

The problems began with the new version. Specifically, so far on at least one computer, it states that "Could not load file or assembly My.dll". This even happens when I have dropped a copy of the software on a network drive and run the software directly from there. It works on every other computer but one, which still gives the exact same error where other computers work fine.

The dll in question is even in the same directory as the executable, so I'm really quite bummed here. I tried to google around a bit as well, but all the issues I found were related to ASP.NET specifically. Any ideas on how to go about finding the problem would be much appreciated.

Have you tried adding a reference to the dll instead of copying it directly in to the bin folder? — Lloyd Powell, May 19 '11 at 10:43
Is the assembly compiled as 32-bit, 64-bit, or Any CPU? What bit-level OS is the computer in question running? — Cody Gray - on strike, May 19 '11 at 10:47
There is a reference to the dll in the project. The assembly is compiled as x86 on an x86 computer. The computer that refuses to work is a x64. However, it has worked on other x64 computers. — bobblez, May 19 '11 at 10:50

score 2 · Answer 1 · answered May 19 '11 at 10:50

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It is possible that the computer in question has a DLL added to it's Global assembly cache. This would take priority over the DLL in the same folder.
More information about the GAC: http://msdn.microsoft.com/en-us/library/yf1d93sz(v=VS.100).aspx

answered May 19 '11 at 10:50

Mr47

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score 1 · Accepted Answer · answered May 19 '11 at 10:50

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Is there an old copy of the DLL lying around? Perhaps with a different name? I had a similar issue when I changed the name of a dll. Internally, the namespaces were the same.

In my case, an older version of the DLL was still there. .NET got confused with two assemblies in the bin directory having the exact same namespaces and classes, couldn't decide on which to load, and threw an exception.

Removing the older version of the dll solved the issue.

answered May 19 '11 at 10:50

Paul Alan Taylor

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Ah this was it, well a combination of this and not using Any CPU as the target platform. On the computer that I could not get to work there was an older version of the dll in another directory, which had been compiled as x86 only. This took precedence over the Any CPU -version and thus broke my things. Thanks a lot to all! – bobblez May 19 '11 at 11:10

score 0 · Answer 3 · answered May 19 '11 at 10:55

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Use the Assembly binding log viewer and set it to log failures. This will give you some clues as to why it is not loading.

answered May 19 '11 at 10:55

AntonyW

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score 0 · Answer 4 · edited May 23 '17 at 11:51

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You could take a look at the error log using the Assembly Binding Log Viewer. First you have to turn on logging.

edited May 23 '17 at 11:51

Community

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answered May 19 '11 at 10:59

Daniel Rose

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score 0 · Answer 5 · answered May 19 '11 at 11:05

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--Right Click on Project --Goto Properties->Build tab --Change Platform and Platform Target to Any CPU, Save and run

answered May 19 '11 at 11:05

ecoGreen

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Debugging "Could not load file or assembly" that only happens on some computers

5 Answers5