Add support for context properties

[isak1080]

In NLog 5 it's possible to add scoped context properties that are automatically attached to all log messages for the lifetime of the scope.

A text-book use case would be in an ASP.Net controller to setup the scope at the beginning of the request, and have all log messages generated within that request to hold some common properties (even if they are not part of the log messages).
This makes it very easy to add things like authenticated username, track "activities" (assign a GUID to each request/operation) etc.

I tested this by cloning this repo and modifying BetterStackLogsTarget.Write() to include the following:

if (IncludeScopeProperties)
{

    var scopeProperties = global::NLog.ScopeContext.GetAllProperties();

    if (scopeProperties != null)
    {
        var scopeDict = new Dictionary<string, object>();

        foreach (var scopeProperty in scopeProperties)
        {
            string key = scopeProperty.Key;
            if (string.IsNullOrEmpty(key)) continue;
            scopeDict[key] = scopeProperty.Value;
        }

        contextDictionary["scope"] = scopeDict;
    }
}

This worked fine in my testing

Note: This would require an update to NLog 5.x (which has been out since 2022)

[PetrHeinz]

Hi @isak1080!

Thank you for raising this and providing a code snippet! 🙌

I've added resolving this into our roadmap. We'll keep you updated here in GitHub.

Thanks again for the report!

[snakefoot]

Notice that you inherit from TargetWithContext, which correctly handles ScopeContext. Where you have access to the following options:

• IncludeEventProperties
• IncludeScopeProperties
• IncludeGdc

protected override void Write(LogEventInfo logEvent) 
{
   IDictionary<string,object> logProperties = this.GetAllProperties(logEvent);
}

See also: https://github.com/NLog/NLog/wiki/How-to-write-a-custom-target-for-structured-logging

I guess when you have your own properties upfront, then you can do this:

        protected override void Write(LogEventInfo logEvent)
        {
            var contextDictionary = new Dictionary<string, object> {
                ["logger"] = logEvent.LoggerName,
                ["properties"] = logEvent.Properties,
                ["runtime"] = new Dictionary<string, object> {
                    ["class"] = logEvent.CallerClassName,
                    ["member"] = logEvent.CallerMemberName,
                    ["file"] = string.IsNullOrEmpty(logEvent.CallerFilePath) ? null : logEvent.CallerFilePath,
                    ["line"] = string.IsNullOrEmpty(logEvent.CallerFilePath) ? null : logEvent.CallerLineNumber as int?,
                },
            };

            contextDictionary = GetAllProperties(logEvent, contextDictionary);

But if you want all "custom" properties include in ["properties"] then this might be better:

        protected override void Write(LogEventInfo logEvent)
        {
            var properties = GetAllProperties(logEvent); // Assign IncludeEventProperties = true in constructor

            var contextDictionary = new Dictionary<string, object> {
                ["logger"] = logEvent.LoggerName,
                ["properties"] = properties,
                ["runtime"] = new Dictionary<string, object> {
                    ["class"] = logEvent.CallerClassName,
                    ["member"] = logEvent.CallerMemberName,
                    ["file"] = string.IsNullOrEmpty(logEvent.CallerFilePath) ? null : logEvent.CallerFilePath,
                    ["line"] = string.IsNullOrEmpty(logEvent.CallerFilePath) ? null : logEvent.CallerLineNumber as int?,
                },
            };