We Keep Coding

Is there something better than preprocessor directives (#if, etc) in C#?

Most questions of this type are seeking to alter the program behavior (things that could be decided at run time) or want to deal directly with debug printing. This is a bit different.
I have code that depends on a peripheral (like a card reader). Sometimes I don't use it, which means the library isn't present. (And I'm being nice, because "library" turns out to mean installing a 2GB software suite). When I remove the library, I can't open the device. If I can't open the device, I can't create the class member that uses it. With the class inoperative, I can't call its methods from within the code. Therefore, I can't just choose not to execute it; I need it to go away since it will not compile without the library.
Preprocessor directives like #if and all that are ok, maybe; but these things appear in more than one file, which means independently maintaining a #define at the top of each. I come from a simpler place (meaning, C) where one header file can be used to control this. I note that C# is rather hostile about #define (either the label exists, or not; no constants or calculations allowed), and that makes me think there's another way.
How do you handle this?
---Follow-up(s)---
I did read the "duplicate" Q/A's, and have a fairly good picture of what I'm dealing with. I didn't find those questions in my original search, but sometimes that's just how it is.
#Amy suggests that #define at the top is "not how it's done" but rather "put it on the command line". So, (if I realize we are sticking with this mechanism) the discussion might go to examining ways to have that happen . One does not simply drop to a terminal and do that. It happens as "IDE features" or "IDE hacks".
#Alexei Levenkov asks what I really want. I really want to (a) not get compile errors, and (b) do it by selectively leaving out the code. And, find the C# equivalent to the way I proposed.
Some more constraints are addressed by the fact that I haven't been using VS or C# for all that long. So I know a lot less than you all do. Considering I got the code from the last person and have to deal with what I see, I don't want to set up the person after me to have to figure out what "interesting" thing I might have done to make it work. Thus, things like hand-editing a project file may work but will also cause consternation down the line.
# Eric Lippert suggests "hostile" is really "sensible". I may have had my tongue too far into my cheek on that one. VS seems to be telling me I'm doing it wrong, so I sensed there's a "right way" I simply don't know about. As for the 2GB supporting application, I will go to various computers and pull down the repository and try out something, and so this "overhead" wants to propagate with it. It's worse if I'm linked through my phone to do the download. And if I build the application with everything included, the end user is then required to install that software suite before the program will run. In theory, they could be required to buy the software. If I sent you a tic-tac-toe game, and told you it wouldn't run until you installed Oracle, you'd probably pass on the whole thing.
I considered the "stub out the interface" idea, but there seemed to be more hooks into the class than I wanted to deal with. Plus, I don't know what these things do, so I have to know something about them in order to "fake" them.
In the end I decided that we're still largely using the #if scheme to get this done, and the replacement feature I imagined might exist, doesn't. And I'm using the provision in the project file(s) as cited by #Jim G. as it gets the job done and is only a little imperfect. It's good enough.

As #BJ Safdie said here:
Set them in your Compilation Properties or Build options.
You get to the build options by right-clicking the project and selecting
properties from the menu.

C# Reading data from Rocksmith's Realtone Cable

I have a bit of an unorthodox question. I am trying to do a little pet project purely out of interest and willingness to mess around for fun and giggles.
I want to read data (bytes, bits or whatever I can) from my rocksmith cable(usb cable attached to a guitar), and just go whack at it in some c# code. I actually have no idea if this is even possible. I have been playing around with libraries such as SharpUsb and LibUsbDotNet, but they don't seem to pick it up as a device, which kindof makes sense.
I also tried using System.IO.Ports.SerialPort, just to see if I can pick up anything but it does not.
So smarter genius people out there. Is this possible ? Any advice/ideas of what I can try ?
Any advice or ideas will be very much appreciated! For me this is purely an out of interest project for fun.
Thanks in advance!

Since the rocksmith Realtone cable is a usb to guitar cable, all you should need the dll file for that piece of hardware and import it into your project / call the proper methods associated with it.
More than likely the code will be in C++, so you will need to use DLLImport function as well.
Any further than that, I'm sure you could figure out where to go from there. You could possibly use XNA and use the microphone class if you have that usb device set as your default microphone, although, that is just a random thought.

Deploying a C# application - user form (novice)

I'm virtually a complete novice, I've tried Googling for answers and become totally confused.
Using Visual Studio 2010, I have a C# application which is an email notifier for a friend. The external (Arduino) hardware works, the main code (from a website) works but I'm sending it to her on the other side of the world to use and she is very 'non-technical' - hence the need for a 'setup form'.
I have created a form where she can enter comm port (selected from a list), username and password (all to be used by the main code), but that form should run only when the application is first installed on the PC.
At the moment it runs in VS-2010 (though I need to iron out a couple of snags), validates and hides - but I don't know how to a) store the data and make it available to the main code, b) ensure that the form only runs at setup, or c) exactly what I need to do or include to create an installable application.
Could somebody either help or direct me to some tutorials that don't assume I understand all the terminology?
I just want to create something that she can instal from a memory stick. I know it can be done and it's proababy quite simple for those who understand - I'm trying to learn but I'm no longer young and it's a struggle.
Thanks

a) store the data and make it available to the main code,
write the data on a file!
you have millions of possibilities, for isntance reading and writing a plain text file can be done with few lines of code, but if you want to encrypt your file (it may be the case if you want to store the password) you can use System.Security.Cryptography as shown in this guide
b) ensure that the form only runs at setup,
once you have written the file, then it means that the program has run already at least once, so you don't need to ask the user again (just read the data from the file)
c) exactly what I need to do or include to create an installable application.
Visual Studio already comes with the Setup project for this task. See this good guide.

From your comment and link to the code project for the Arduino, I gather that this is your first venture into writing code in C#, or very close to it. And ideally you'd like to make this as easy for your friend as possible. The best advice I can give you is not to try to run before you learn to walk. If you try to create a custom setup project and use a configuration file, which is what you are talking about doing, you may hit so many barriers that you never get to a successful end of the project. That kind of experience is discouraging and I'd hate for you to lose the drive to ever want to try another software project.
Make this initial project easy on yourself. This is not good programming practice for most situations, but if you only have one user, hard-code her configruation information for this first version. In other words, put her username, password, com port, etc directly into the main program. This eliminates the need for both the configuration, and any custom setup form. If you still want to make the whole thing configurable and versatile, do that in your next version. Custom setup is not a beginner task. It will be a lot easier to take on with the encouragement of your friend's excitement and compliments over a first version that works.

Make an executable at runtime

Ok, so I was wondering how one would go about creating a program, that creates a second program(Like how most compression programs can create self extracting self excutables, but that's not what I need).
Say I have 2 programs. Each one containing a class. The one program I would use to modify and fill the class with data. The second file would be a program that also had the class, but empty, and it's only purpose is to access this data in a specific way. I don't know, I'm thinking if the specific class were serialized and then "injected" into the second file. But how would one be able to do that? I've found modifying files that were already compiled fascinating, though I've never been able to make changes that didn't cause errors.
That's just a thought. I don't know what the solution would be, that's just something that crossed my mind.
I'd prefer some information in say c or c++ that's cross-platform. The only other language I'd accept is c#.
also
I'm not looking for 3-rd party library's, or things such as Boost. If anything a shove in the right direction could be all I need.
++also
I don't want to be using a compiler.
Jalf actually read what I wrote
That's exactly what I would like to know how to do. I think that's fairly obvious by what I asked above. I said nothing about compiling the files, or scripting.
QUOTE "I've found modifying files that were already compiled fascinating"
Please read and understand the question first before posting.
thanks.

Building an executable from scratch is hard. First, you'd need to generate machine code for what the program would do, and then you need to encapsulate such code in an executable file. That's overkill unless you want to write a compiler for a language.
These utilities that generate a self-extracting executable don't really make the executable from scratch. They have the executable pre-generated, and the data file is just appended to the end of it. Since the Windows executable format allows you to put data at the end of the file, caring only for the "real executable" part (the exe header tells how big it is - the rest is ignored).
For instance, try to generate two self-extracting zip, and do a binary diff on them. You'll see their first X KBytes are exactly the same, what changes is the rest, which is not an executable at all, it's just data. When the file is executed, it looks what is found at the end of the file (the data) and unzips it.
Take a look at the wikipedia entry, go to the external links section to dig deeper:
http://en.wikipedia.org/wiki/Portable_Executable
I only mentioned Windows here but the same principles apply to Linux. But don't expect to have cross-platform results, you'll have to re-implement it to each platform. I couldn't imagine something that's more platform-dependent than the executable file. Even if you use C# you'll have to generate the native stub, which is different if you're running on Windows (under .net) or Linux (under Mono).

Invoke a compiler with data generated by your program (write temp files to disk if necessary) and or stored on disk?
Or is the question about the details of writing the local executable format?

Unfortunately with compiled languages such as C, C++, Java, or C#, you won't be able to just ``run'' new code at runtime, like you can do in interpreted languages like PHP, Perl, and ECMAscript. The code has to be compiled first, and for that you will need a compiler. There's no getting around this.
If you need to duplicate the save/restore functionality between two separate EXEs, then your best bet is to create a static library shared between the two programs, or a DLL shared between the two programs. That way, you write that code once and it's able to be used by as many programs as you want.
On the other hand, if you're really running into a scenario like this, my main question is, What are you trying to accomplish with this? Even in languages that support things like eval(), self modifying code is usually some of the nastiest and bug-riddled stuff you're going to find. It's worse even than a program written completely with GOTOs. There are uses for self modifying code like this, but 99% of the time it's the wrong approach to take.
Hope that helps :)

I had the same problem and I think that this solves all problems.
You can put there whatever code and if correct it will produce at runtime second executable.
--ADD--
So in short you have some code which you can hard-code and store in the code of your 1st exe file or let outside it. Then you run it and you compile the aforementioned code. If eveything is ok you will get a second executable runtime- compiled. All this without any external lib!!

Ok, so I was wondering how one would
go about creating a program, that
creates a second program
You can look at CodeDom. Here is a tutorial

Have you considered embedding a scripting language such as Lua or Python into your app? This will give you the ability to dynamically generate and execute code at runtime.
From wikipedia:
Dynamic programming language is a term used broadly in computer science to describe a class of high-level programming languages that execute at runtime many common behaviors that other languages might perform during compilation, if at all. These behaviors could include extension of the program, by adding new code, by extending objects and definitions, or by modifying the type system, all during program execution. These behaviors can be emulated in nearly any language of sufficient complexity, but dynamic languages provide direct tools to make use of them.

Depending on what you call a program, Self-modifying code may do the trick.
Basically, you write code somewhere in memory as if it were plain data, and you call it.
Usually it's a bad idea, but it's quite fun.

NOVAS for .NET

Any astronomers out there? I'm wondering if anyone has produced or stumbled upon a .NET (preferably C#) implementation of the US Naval Observatoru Vector Astrometry Subroutines (NOVAS).

I know nothing (of consequence) about astronomy, and absolutely nothing about NOVAS, so please take this with a grain of salt.
But, I did look at the website, and it looks like they have a C implementation. You could always take the C implementation, access it via pinvoke, and write a C# wrapper around it.

Are you only interested in a port of that library or anything usable from C# for astronomy?
I don't have anything for the first part, but for the second I would take a look at AGI's Components. Their libraries provide ways to compute all kind of astronomical data. The Dynamic Geometry Library lets you model everything including planets and such rather easily.

This download contains a very useful astronomical library in C#.
Sorry that I don't remember where I got it but perhaps it is documented in there somewhere.
http://www.planet-source-code.com/vb/scripts/ShowCode.asp?txtCodeId=8399&lngWId=10
Sidenote: The NOVAS library is not very complete. You would be better off to pursue the SOFA lib from the International Astronomy Union. Here's the link:
http://www.iausofa.org/

Urania is an astronomy library in C#:
http://www.smokycogs.com/blog/tutorials/astronomical-calculations-in-c-sharp/
The download is the non-obvious "here" link on the page that combines all of the sample code into a single app called Urania.
Once downloaded, you will also need to modify the Urania.sln file to fix the paths of the different libraries that he uses (MathLib, UraniaLib, etc.) and then it will compile correctly. (Open Urania.sld in notepad and delete: "..\Libs\" out of the 3 project paths)