Question

I need to Log messages only when application is running in debug mode. I have found 2 ways:

First: Need to write 3 lines everywhere when logging is needed. But, Logger statement is disabled at compile time only which is exactly I need. Logger.Log will not be executed at all.

#if DEV_ENV
        Logger.Log("Application started !"); // This line is grayed. Perfect !
#endif

public static void Log(string message)
{
    Debug.WriteLine(message);
}

Second: Very neat. Only one line of code wherever logging is required. Not sure, whether Logger.Log statement is executed or not. If function call is removed at compile time only (same as first approach. But, now sure as line of code is not greyed out), I want to go with this.

Logger.Log("Application started !"); // This line is not grayed out. But, function is not called. So, confused whether its removed at compile time.

[Conditional("DEV_ENV")]
public static void Log(string message)
{
    Debug.WriteLine(message);
}

I am concerned about the performance differences.

Answer 1

From the MSDN page for the ConditionalAttribute:

Applying ConditionalAttribute to a
method indicates to compilers that a
call to the method should not be
compiled into Microsoft intermediate
language (MSIL) unless the conditional
compilation symbol that is associated
with ConditionalAttribute is defined.

So, as it says, the method call is removed at compile time, same as the #if.