Referencing 2 different versions of log4net in the same solution

I found the solution by using this answer to a similar question

You create 2 folders in your project one for each version of log4net. 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.

Then you modifiy the app.config file by adding something like this:

<configuration>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="log4net" publicKeyToken="681549d62126b7b8" />
        <codeBase version="1.2.9.0" href="https://stackoverflow.com/questions/3158928/log4netv1.2.9.0\log4net.dll" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="log4net" publicKeyToken="1b44e1d426115821" />
        <codeBase version="1.2.10.0" href="log4netv1.2.10.0\log4net.dll" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="log4net" publicKeyToken="669e0ddf0bb1aa2a" />
        <codeBase version="1.2.11.0" href="log4net.dll" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
</configuration>

you can get the public key token of an assembly by using sn -T [assemblyName]