How do I stop Nhibernate log4net conflicting with existing log4net?

Question

I'm very new to this so I apologise if my question isn't well structured or just in the wrong place, etc. I've had a good look for solutions to this and tried a number of different approaches but haven't found anything that works so....

I have a solution that makes use of Nhibernate, and consequently must use log4net V1.2.10.0, which comes in the log4net/2.0/ folder. However my solution also links to a number of other solutions, to which I have very limited access. These make use of the same log4net V.1.2.10.0 but in folder: log4net/1.2/

When I run my solution I get this error.

{"Could not load file or assembly 'log4net, Version=1.2.10.0, Culture=neutral, 
PublicKeyToken=e27b8fa57f63a98d' or one of its dependencies. The located assembly's 
manifest definition does not match the assembly reference. (Exception from HRESULT: 
0x80131040)":"log4net, Version=1.2.10.0, Culture=neutral, 
PublicKeyToken=e27b8fa57f63a98d"}

I have tried to amend the solutions that it is calling, however each time I amend one I get the error within that solution as soon as it tries to use another solution, so I have to amend another and so on. There are simply too many solutions to amend and too many interdepencies with other solutions that I have absolutely no control over for me to be able to change them all so that they use log4net/2.0.

I have found another question ( Referencing 2 different versions of log4net in the same solution ) which I think is basically the same problem, and they amend the app.config with a binding, however I can't seem to get this right, as I'm still getting the same error. The binding I've included in my app.config is this:

<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
  <dependentAssembly>
    <assemblyIdentity name="log4net" publicKeyToken="e27b8fa57f63a98d" />
    <codeBase version="1.2.10.0" href="2.0\log4net.dll" />
  </dependentAssembly>
  <dependentAssembly>
    <assemblyIdentity name="log4net" publicKeyToken="1b44e1d426115821"/>
    <codeBase version="1.2.10.0" href="1.2\log4net.dll" />
  </dependentAssembly>
 </assemblyBinding>
</runtime>

I'm not sure what the answer to the other question means when it says "You create 2 folder in your project one for each version of log4net. You place each log4net.dll in its corresponding folder by adding an the file to the solution (not with add reference). You can set the copy to output directory property to copy always so that it is automatically copied to the output folder when you build." And would I need to do this to every solution that my solution references?

Ideally I want to be able to make an amendment to my solution which simply means that it doesn't care what log4net any of the solutions are using but they can still pass log messages between each other. I assume this is possible, so any help would be hugely appreciated. Either that or how do I turn off nHibernate's logger so that it doesn't care what log4net I'm using so I can just continue to use the log4net/1.2 that all the other solutions are using. I've tried all sorts of things to turn it off but it still seems to end up trying to find the log4net/2.0.

Answer 1

You're lucky in that you've got the same DLL in two different places, which makes your problem easier to solve. You could simply take a back up and then delete one of the references of the DLL (the \1.2\ version?) and then resolve any broken references in your solution - that should get you to a point that you can compile.

Have you tried NuGet too? You could add a reference to Log4Net and then add a reference to Nhibernate, which would see that you've already satisfied it's dependency requirement and would not need to download another reference to NHibernate.

I'd recommend the learning curve of using NuGet because it is a powerful tool that should make your life much easier in the long run.

Update Please see my comment about providing your current folder structure to help - incase you can do that; the following should get you started.

To try and do this using just direct file references you may need to move your DLL's around into a better structure. Inside your solution (not project) create the following folder structure under solution items.

\ExternalReferences \Log4Net\ \NHibernate\

Move a single copy of the log4net DLL inside the log 4 net folder (and delete the other instance) and then move all the NHibernate DLL's you are using (minus Log4Net) in the NHibernate directory. Remove the bindings inside your app.config and then go through each project updating the references to point to the version inside the external references.

The actual location of the files isn't that important, you just need your code to reference a single instance of the DLL and then when it builds they all get copied into the bind folder. You're just running into problems because you have two instances - whilst you are editing your code, etc. NHibernate isn't actually too bothered where Log4Net is; it just has a dependency on it that must be forfilled when it runs.

Update 2

New Version of Log4Net on NuGet that breaks backward compatibility - see the referenced blog post for more info. There is now a 1.2.11.0 version of Log4Net that contains a different strong name to 1.2.10.0, making things just that little harder!