Your config file seems correct. Then, you have to register your Log4net config file to application. So you can use below code:
var logRepo = LogManager.GetRepository(Assembly.GetEntryAssembly());
XmlConfigurator.Configure(logRepo, new FileInfo("log4net.config"));
After registering process, you can call below definition to call logger:
private static readonly ILog log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
log.Error("Sample log");