Formatting.md

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Formatting Logs

By implementing the RockLib.Logging.ILogFormatter interface, defining the Format method, and providing it to a log provider (such as a FileLogProvider, a ConsoleLogProvider or a RollingFileLogProvider), you are able to transform a LogEntry object into a string emitted by the log provider.

As an example, the following implementation of ILogFormatter will output LogEntry.Message followed by the Log LogEntry.CreateTime, with each separated by a hyphen.

public class SimpleMessageFormatter : ILogFormatter
{
	public string Format(LogEntry logEntry)
	{
		// output Message - CreateTime (in ISO8601 format)
		return $"{logEntry.Message} - {logEntry.CreateTime.ToString("o")}";
	}
}

This would result in the following message being output by the consuming log provider when it is prompted to log:

SAMPLE LOG MESSAGE - 2025-06-10T16:20:57.7876207Z

Log formatters are passed to the Log provider via the constructor. For example, the following code will provide a new instance of the above message formatter to a new FileLogProvider:

var fileLogProvider = new FileLogProvider("log.txt", new SimpleMessageFormatter());