This is the ModPath + the filename of your DLL. This can either be under %AppData% (when compiling and running locally) or under the 'SteamApps' folder (if installed via the Steam workshop). The path is the location where your library is located.
It is also absolutely important you version your library using AssemblyVersionAttribute, otherwise the plugin resolving code won't work properly and might return the wrong mod location.
Use of this base class is only working for compiled class library projects. You do not have to implement IUserMod, this class will use the provided info in the Assembly attributes to report the mod information to the game. If you followed all the steps above correctly, you can simply create your plugin class now and inherit from ModBase. This ModBase class is an abstract class that implements IUserMod for you. Note: I choose not to copy using post-build event to this folder automatically. You can now publish an update via the Content Manager. Find your own mod and copy the updated files in here. In that folder each mod will have its own folder id. You receive your mod back but now in a new location:
After publishing to the Steam Workshop, you should subscribe to your own mod. Once you have developed your first working plugin, you will want to publish to the Steam Workshop via the ingame Content Manager.
Please check out my implementation of the Autosave mod for details on how to use these 3 classes. You are now done setting up the project and can start coding your plugin. Md " %appdata%\.\Local\Colossal Order\Cities_Skylines\Addons\Mods\$(TargetName) " xcopy "$(TargetDir)*.* " " %appdata%\.\Local\Colossal Order\Cities_Skylines\Addons\Mods\$(TargetName) " /Y /E Rd " %appdata%\.\Local\Colossal Order\Cities_Skylines\Addons\Mods\$(TargetName) " /s/q