I was developing for .NET core 2.1 using log4net 2.0.8 and found NealWalters code moans about 0 arguments for XmlConfigurator.Configure(). I found a solution by Matt Watson here
log4net.GlobalContext.Properties["LogFileName"] = @"E:\\file1"; //log file path
var logRepository = LogManager.GetRepository(Assembly.GetEntryAssembly());
XmlConfigurator.Configure(logRepository, new FileInfo("log4net.config"));