How to use code mode to add fields

[silvmind]

var config = new LoggingConfiguration();
var mongoTarget = new MongoTarget();
 config.AddTarget("targetMongo", mongoTarget);

nlog.config
<field name="AppName" layout="${AppName}"/>

[snakefoot]

You can do this::

var config = new LoggingConfiguration();
var mongoTarget = new NLog.Mongo.MongoTarget();
mongoTarget.Fields.Add(new NLog.Mongo.MongoField() { Name = "AppName", Layout = "${AppName}" });
config.AddTarget("targetMongo", mongoTarget);