ConditionalAttribute

#define CONDITION1
#define CONDITION2

using System;
using System.Diagnostics;

class Test
{
    static void Main()
    {               
        Console.WriteLine("Calling Method1");
        Method1(3);
        Console.WriteLine("Calling Method2");
        Method2();

        Console.WriteLine("Using the Debug class");
        Debug.Listeners.Add(new ConsoleTraceListener());
        Debug.WriteLine("DEBUG is defined");
    }

    [Conditional("CONDITION1")]
    public static void Method1(int x)
    {
        Console.WriteLine("CONDITION1 is defined");
    }

    [Conditional("CONDITION1"), Conditional("CONDITION2")]  
    public static void Method2()
    {
        Console.WriteLine("CONDITION1 or CONDITION2 is defined");
    }
}

https://msdn.microsoft.com/en-us/library/system.diagnostics.conditionalattribute.aspx