How to include logging scope into the log file using NLog

Question

I'm using NLog.Extensions.Logging.

When registering a logger factory using the method AddNLog(), it is possible to enable logging scope using NLogProviderOptions.IncludeScopes.

But how to make NLog write logging scope to a file?

I haven't found anything similar in the list of available layouts

Lindbom

Does this post help: learn.microsoft.com/en-gb/aspnet/core/fundamentals/logging/…? – Treharne

@MikeParkhill unlikely, he asking how to write which scope is being used in the log, not how to use scoped logging – Frank

yeah, that post calls out that it will be included in the log if configured properly - thought it might help them see what they're missing – Treharne

If you just want to add an additional logevent property, then this might be of interest: github.com/NLog/NLog.Extensions.Logging/wiki/… – Shotton

Answer 1

An example:

Log like this:

// logger is here of type Microsoft.Extensions.Logging.ILogger
using (logger.BeginScope(new[] { new KeyValuePair<string, object>("userid", request.UserId) }))
{
   logger.LogDebug("My log message");
}

Render like this: ${mdlc:userid}.

For example in the file target:

 <target name="file" xsi:type="File"
     layout="${longdate} ${logger} ${message}${exception:format=ToString}, user: ${mdlc:userid}" 
     fileName="${basedir}/${shortdate}.log" />

Note: NLogProviderOptions.IncludeScopes is enabled by default.

NLog directly

The syntax is a bit clumsy, but that is because Microsoft's abstraction is a bit limited. See also this issue: .NET - Logging structured data without it appearing in the text message

If you refer NLog directly, you could also do:

using (NLog.MappedDiagnosticsLogicalContext.SetScoped("userid", request.UserId))
{
   // logger here of type NLog.Logger
   logger.Info("My log message");
}

Also this is rendered with ${mdlc:userid}

More examples and different scopes for NLog explained here

Docs

PS: I have updated available layouts, so you could find it easier :)

Dishearten

It isn't necessary to pass the KeyValuePair array when creating a scope. I'm using template string with params, and it works well. Like this: logger.BeginScope("{userid}", request.UserId) – Libidinous

Answer and docs uses different syntax. So its ${mdlc:userid} or ${mdlc:item=userid}? – Winker

Both are fine. item is the default for this renderer, so you could skip it – Dishearten

With NLog 5, MDLC has been replaced by ScopeProperty github.com/NLog/NLog/wiki/ScopeProperty-Layout-Renderer – Enunciation

Answer 2

New (in V5) is to use ${scopenested}.

See https://github.com/NLog/NLog/wiki/ScopeNested-Layout-Renderer.

Palliasse