06 Adding Custom Data

Adding custom data to your messages is easy if you log messages with an Exception class or a custom class that inherits from Exception.

If you log messages using the method signature:

_log.Error("System Error", new Exception("Something terrible happened."));

it will cause the Exception{} array to be populated in the Elasticsearch document. Since Exception has a built in Data property which is a dictionary that can be added to, you can create an Exception instance and add custom properties to the dictionary:

// Log an exception object with custom fields in the Data property
Exception newException = new Exception("There was a system error");
newException.Data.Add("CustomProperty", "CustomPropertyValue");
newException.Data.Add("SystemUserID", "User43");

_log.Error("Something broke.", newException);

{
	"_index": "log-2016.02.12",
	"_type": "logEvent",
	"_id": "AVLXHEwEJfnUYPcgkJ5r",
	"_version": 1,
	"_score": 1,
	"_source": {
		"timeStamp": "2016-02-12T20:11:41.5864254Z",
		"message": "Something broke.",
		"messageObject": {},
		"exception": {                                          <-- Exception Object
			"Type": "System.Exception",
			"Message": "There was a system error",
			"HelpLink": null,
			"Source": null,
			"HResult": -2146233088,
			"StackTrace": null,
			"Data": {
				"CustomProperty": "CustomPropertyValue",        <-- Custom field data
				"SystemUserID": "User43"                        <-- Custom field data
			},
			"InnerException": null
		},
		"loggerName": "log4net.ES.Example.Program",
		"domain": "log4net.ES.Example.vshost.exe",
		"identity": "",
		"level": "ERROR",
		"className": "log4net.ES.Example.Program",
		"fileName": "C:\\Users\\jtoto\\projects\\log4net.ES.Example\\log4net.ES.Example\\Program.cs",
		"lineNumber": "26",
		"fullInfo": "log4net.ES.Example.Program.Main(C:\\Users\\jtoto\\projects\\log4net.ES.Example\\log4net.ES.Example\\Program.cs:26)",
		"methodName": "Main",
		"fix": "LocationInfo, UserName, Identity, Partial",
		"properties": {
			"log4net:Identity": "",
			"log4net:UserName": "JToto",
			"log4net:HostName": "JToto01",
			"@timestamp": "2016-02-12T20:11:41.5864254Z"
		},
		"userName": "JToto",
		"threadName": "9",
		"hostName": "JTOTO01"
	}
}

You can see this example in action in the sample application.