NLogEx is described as 'A lightweight logging framework for .NET 4.0+'. There are five alternatives to NLogEx for a variety of platforms, including Mac, Windows, Linux, Online / Web-based and.NET Framework. The best alternative is Raygun. It's not free, so if you're looking for a free alternative, you could try log4net or ELMAH. Other great apps like NLogEx are elmah.io (Paid) and OneTrueError (Free Personal).
ELMAH (Error Logging Modules and Handlers) is an application-wide error logging facility that is completely pluggable. It can be dynamically added to a running ASP.NET web application, or even all ASP.
May be the coolest cloud based error logger for .NET web applications. Based on the de-facto standard error component ELMAH, logging errors from your webserver requires nothing more than installing a NuGet package.