IsDebugEnabled vs. Debugging (Action <FormatMessageHandler>)

Question

In the general V2.0 protocol, there are two ways to avoid the cost of evaluating messages when LogLevel is higher than the log entry:

if (Log.IsDebugEnabled)
    Log.Debug("Debug message");

or

Log.Debug(a => a("Debug message"));

Which practice is better? What are the pros and cons?

Answer 1

According to the documentation:

Using lambdas, the ILog interface offers a new and secure way to record statement logs

log.Debug( m=>m("value= {0}", obj.Value) );

This ensures that the whole expression is evaluated only when LogLevel.Debug is turned on and therefore eliminates the need to write

if (log.IsDebugEnabled)
{
    log.Debug("value={0}", obj.Value);
}

to avoid this overhead.

So, the second option in your quesetion is considered best practice.