What should I change when the compiler tells me to "Consider app.config remapping" when I have no app.config file?

Question 1

You can add an app.config file and then map the libraries like this:

  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="dotless.ClientOnly" publicKeyToken="96b446c9e63eae34" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-1.3.1.0" newVersion="1.3.1.0" />
      </dependentAssembly>

Question 2

Please use Auto-generate binding redirects at project properties window in Visual Studio

Question 3

I have just fixed this error really simple. Close your project. Open again.Go to NuGet Packages for solutions. You will have a section there Consolidate. Just near search tool. Go there and choose what version you want to use. Also make sure that all your projects have the same version. Then inside all solutions add missing libraries before your namespace. Now compile your project and I hope it will start working again.

Question 4

I added an app.config file with this code, and my compile time is now 1/3 of what it was. This was for System.Data

<configuration>
    <runtime>
        <assemblybinding xmlns="urn:schemas-microsoft-com:asm.v1">
            <!-- 2.0 to 3.5 -->
            <dependentassembly>
                <assemblyidentity culture="neutral" publickeytoken="969db8053d3322ac" name="System.Data" />
                <bindingredirect newVersion="3.5.0.0" oldVersion="2.0.0.0" />
            </dependentassembly>

            <!-- 1.0 to 3.5 -->
            <dependentassembly>
                <assemblyidentity culture="neutral" publickeytoken="969db8053d3322ac" name="System.Data" />
                <bindingredirect newVersion="3.5.0.0" oldVersion="1.0.5000.0" />
            </dependentassembly>
        </assemblybinding>
    </runtime>
</configuration>

I found this code here: http://grenangen.se/node/25#comment-1003

Question 5

In my case the following warning was shown in the Output window:

11>  Consider app.config remapping of assembly "log4net, Culture=neutral, PublicKeyToken=669e0ddf0bb1aa2a" from Version "1.2.15.0" [] to Version "2.0.12.0" [C:\s\[SolutionName]\log4net.dll] to solve conflict and get rid of warning.
11>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets(2182,5): 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="0.0.0.0-2.0.12.0" newVersion="2.0.12.0" /></dependentAssembly></assemblyBinding>

When I clicked this warning in the Output window "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets" file opened. I was surprised I should change something what is outside of my solution folder. Another surprise was I should change app.config even I worked on the web service with web.config configuration file. Programmers probably didn't realized that this warning shows also for services...

Anyway, double-click on this warning in the Error List window, not in the Output window. Be sure your Warnings button at the top of the Error List window is pressed so you can see this warning in the Error List Window. This way you should solve this warning by proper way.

What should I change when the compiler tells me to "Consider app.config remapping" when I have no app.config file?

UPDATE

UPDATE 2