How do I set a conditional compile variable?
<p>In C/C++ you can define macros in code like this:</p>

<pre><code>#define OLD_WAY  1
</code></pre>

<p>Although I've never done it, I assume that the same thing is available in C#.  More to the point, in C/C++ it is possible to then do some conditional compilation logic by doing something like this:</p>

<pre><code>#if OLD_WAY == 1
 int i = 0;
#else
 int i = 1;
#endif
</code></pre>

<p>OK, so this is all cool and all that.  And again, I assume that such logic is possible within C#.  What I'd like to know is, how do I define constants at the project level, so that I can put in logic that will allow me to conditional compile one block of code if I define the constant one way, or another block of code if I don't define it that way?  I'm assuming that it's done somewhere in the project's properties, but how and where do I define it?</p>
