This post shows you how to fix 'Consider app.config remapping of assembly "log4net, Culture=neutral, PublicKeyToken=669e0ddf0bb1aa2a" from Version 2.0.9.0" [...\log4net.dll] to Version "2.0.11.0" [...\packages\log4net.2.0.11\lib\net45\log4net.dll] to solve conflict and get rid of warning.'

C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\15.0\Bin\Microsoft.Common.CurrentVersion.targets(2110,5): warning MSB3247: Found conflicts between different versions of the same dependent assembly. In Visual Studio, double-click this warning (or select it and press Enter) to fix the conflicts; otherwise, add the following binding redirects to the "runtime" node in the application configuration file: <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"><dependentAssembly><assemblyIdentity name="log4net" culture="neutral" publicKeyToken="669e0ddf0bb1aa2a" /><bindingRedirect oldVersion="0.0.0.0-2.0.11.0" newVersion="2.0.11.0" /></dependentAssembly></assemblyBinding>

Opening your web.config, then modify your configuration as shown below.

<runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="log4net" publicKeyToken="669e0ddf0bb1aa2a" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-2.0.9.0" newVersion="2.0.11.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>

You need to specify the library version you want to use.