How to get the version of the .NET Framework being targeted? [duplicate]

Answer 1

What prevents you from using an ordinary /define?

csc /define:NET45 /optimize /out:MyProgram.exe *.cs

with

using System;
public class Test 
{
    public static void Main() 
    {
        #if (NET45) 
            Console.WriteLine("NET45 targeted");
        #else
            Console.WriteLine("NET45 not targeted");
        #endif
    }
}

Answer 2

That's simple - check the TargetFrameworkAttribute:

var targetFrameworkAttribute = Assembly.GetExecutingAssembly()
    .GetCustomAttributes(typeof(System.Runtime.Versioning.TargetFrameworkAttribute), false)
    .SingleOrDefault();