Preprocessor directives vs. Conditional Attributes

This is a simple example where you can see proprocessor directive and also Conditional Attribute.

Code Snippet

     class Program

2. {
3.    static void Main(string[] args)
4.    {
5.  
6. # if DEBUG
7.      Console.WriteLine("Application starts in debug mode");
8. # else
9.     Console.WriteLine("Application starts NOT in debug mode");
10. # endif
11.  
12.      SayHelloOnlyInDebug();
13.  
14.      Console.ReadLine();
15. }
16.  
17.  [Conditional("DEBUG")]
18.   private static void SayHelloOnlyInDebug()
19.   {
20.     Console.WriteLine("Hello!");
21.   }
22. }

       

And what is  different between  proprocessor directive and Conditional Attribute?
Proprocessor directive - the statement in #if #else is compiled conditionally dependent upon thepresence of the DEBUG symbol. 

Conditional Attribute - You might feel more comfortable with the Conditional attribute, which can be used to exclude entire methods, without needing to complicate the source with conditionals on the calling side.