Develop Reference

Creating .Net Wrappers for Windows API and COM DLLs

Let me start by saying that I don't know what I don't know at this point, so rather than specific answers, I'm also looking for better questions to ask, I think. My .Net/C# is solid enough, and my C/C++ is meh.
Lately, I'm finding that there are no libraries in the standard .Net framework to accomplish certain tasks, and while it's easy enough to download a third party library, I'd like to understand how to do it myself if one doesn't already exist.
In one recent case, I need to deal with MIDI in windows at a relatively low-level, and I accidentally found out that "winmm.dll" is the library I'll need to use by downloading a .net wrapper for MIDI and browsing through the source. I understand that I'll have to make a wrapper class and do the whole P/Invoke thing to make that happen.
The next thing I did was to search for documentation on the Windows API to figure out what was going on in the mystery box of "winmm.dll," and to my delight, there was a whole Windows SDK that I was able to download and read through. I went through the "getting started" section of "Windows Development" which covered some of the basics via C++. It talked a bit about COM, windows header files, and I know enough C++ to get the gist.
Now, I need help connecting the dots on a few issues:
1) The Windows SDK, so far, seems to suggest that I want to program to specific header files rather than the dlls themselves, but the .net wrappers I've found typically point to a specific .dll rather that a header file...
/// <summary>
/// Returns the number of MIDI input devices on this system.
/// </summary>
/// Win32 docs: http://msdn.microsoft.com/en-us/library/ms711608(VS.85).aspx
[DllImport("winmm.dll", SetLastError = true)]
public static extern UInt32 midiInGetNumDevs();
I was under the impression that a header file and DLL needed to be in the same folder, but the windows SDK includes a folder with all the windows header files, and no DLLs (I'm guessing the registry comes into play here for mapping to specific libraries?)? How do those header files eventually get mapped to actual libraries, and why does it seem like I don't even need to deal with header files to create a .Net wrapper?
2) I can't seem to find documentation on winmm.dll, but I have found references to the functions I'll likely need in the "Windows API" list in the Windows SDK, and I'm pretty sure that the code for those functions are in winmm.dll. How do I find the documentation for the specific libraries I'll need to begin creating my wrapper? If I didn't know that I was going to need winmm.dll to access windows MIDI functionality, how could I have figured that out myself?
3) Some DLLs are COM, some are plain windows DLLs, some are .net DLLs... how can I tell the different going forward? It seems that creating wrappers for the former two would require a different approach.
4) There is no page on MSDN for "Winmm.dll" listing all of its API, and I assume there's a good and practical reason for that, but I'm not sure what it is? I'm used to .Net land where I can figure out what a library does and how to use it almost without effort.
Thanks in advance for any insights.

The bible on this is Adam Nathans excellent book '.Net and COM the complete interoperability guide'
Includes PInvoke and several audio-type examples

1) The windows API documentation includes the header, library, and dll file for each method/enum/etc. I just didn't scroll down far enough when I read through to notice this. A header file doesn't necessarily have to be in the same directory as the dll; its contents are simply copy/pasted into the .c file when the program is compiled. The part I was missing here was the linking stage of compilation which I read about here
2) The documentation was there--I just had to look for it a little bit harder.
3) How can I detect the type of a dll? (COM, .NET, WIN32)
4) The api for audio could theoretically span multiple dlls, so the best course of action is to find the API documentation, find the methods you want to wrap, then figure out what dlls those methods are in, and then import each of those DLLs.

Hiragana to Kanji converter

do you know if there is a library in C# or a dictionary that could help me to translate Hiragana to Kanji?
I know that there is the IME of Windows but I would like to customize entirely the design of the candidate list of Kanji for a given Hiragana and it is not possible with this IME.
Exemple : the user writes "toru", first it is translated in Hiragana : "とる"
I would like to have this list of choice:
撮る
取る
盗る
Thanks!

Unfortunatelly I do not know of a c# library. All I found involves importing some native libraries, like in this OS thread: Japanese to Romaji with Kakasi
If you are willing to do so, perhaps JWPce might help.
Although this is implemented as a Japanese text editor, it also contains a dictionary function (it actually contains a multitude of character lookup systems) that do what you want to do.
Possibly you can compile the project and then import those lookup functionality? JPWce is licensed under GPL and you can download both a binary executable and source code directly available from the homepage.
[Edit]
Researching some more I stumbled over mozc at Google Code:
Mozc is a Japanese Input Method Editor (IME) designed for
multi-platform such as Chromium OS, Windows, Mac and Linux. This
open-source project originates from Google Japanese Input.
(BSD license)
I have not looked into it myself yet, but it might be more what you are looking for as it does not have a full application "around it" but instead is intended to be used a library. Just like you wanted.
They also link to a short video how the input looks like: http://www.google.co.jp/ime/
Unfortunatelly, this still is C++, not .NET but it might be a starting point.

Microsoft publishes this as a separate product, called Visual Studio International Pack
http://visualstudiogallery.msdn.microsoft.com/74609641-70BD-4A18-8550-97441850A7A8

I do not know a C# library either. But given that a dictionary might be sufficient, you may want to look into using the IME dictionary that comes with Anthy.
If you download the sources of the most recent version, you'll find dictionary sources in the mkworddic and alt-cannadic directories. Look at the various files ending in .t.
Note that they are encoded in EUC-JP; you might want to convert them to UTF-8.

Accessing Windows API Constants and Structs for P/Invoke

Quick question: How can I access the BN_CLICKED constant and other constants defined for the Win32 API from .NET? Are they defined in some library? Do I have to define them myself? If so, where can I find these values? And are the values version-specific between versions of Windows?

I find the PInvoke Interop Assistant to be really helpful:
http://blogs.microsoft.co.il/blogs/sasha/archive/2008/01/12/p-invoke-signature-generator.aspx.
It has almost everything and can convert the C++ to C#/VB for you. I rarely, if ever, resort to searching google/pinvoke.net anymore.
Here's the MSDN Magazine Article: http://msdn.microsoft.com/en-us/magazine/cc164193.aspx
The original January 2008 MSDN Magazine Article is now only available as a .CHM help file download, linked from the very bottom of https://msdn.microsoft.com/magazine/msdn-magazine-issues. (Column "CLR Inside Out: Marshaling between managed and unmanaged code.")
And here's the download: http://download.microsoft.com/download/f/2/7/f279e71e-efb0-4155-873d-5554a0608523/CLRInsideOut2008_01.exe. The source code can be found at http://clrinterop.codeplex.com/.

You could download the Microsoft Platform SDK and take a look at the header files (*.h). E.g. the BN_CLICKED is defined in the winuser.h file.
Usually, if you just need one or two constants, a Google search and a look at the first few results is also sufficient, since the value is printed there.

http://pinvoke.net/ is an excellent resource for this many common P/Invoke definitions.

The MagNumDB website (by SO user Simon Mourier) is an easy way to look up constants:
http://www.magnumdb.com/search?q=BN_CLICKED

It's kind of a proof-of-concept, but I put together a script that can look up most any Windows API constant. Example usage:
PS > .\Get-WindowsSDKConstant.ps1 BN_CLICKED
0
PS > .\Get-WindowsSDKConstant.ps1 BN_DBLCLK
5
PS > .\Get-WindowsSDKConstant.ps1 WM_COMMAND
273
It requires you to download Visual Studio and the Windows 10 SDK, because behind-the-scenes it compiles a program that looks up the constant.
Finally, here's some answers to the asker's questions:
Are [the constants] defined in some library?
The authoritative source is the Windows Platform SDK
Do I have to define them myself?
They're not built-in to Windows or .NET, which means you'll probably define them yourself (or copy them from somewhere).
And are the values version-specific between versions of Windows?
They're very stable, because otherwise a program compiled for one version of Windows might stop working when a user upgrades to a newer version of Windows. Microsoft goes to great lengths to prevent this from happening.
However, I've seen at least one place where the constants are different depending on what platform/architecture you're compiling on. I wouldn't assume that just because your code works on x86 64-bit Windows, it'll work on ARM 32-bit Windows RT, for example.

Can you access standard Windows strings like 'Cancel'?

I am building a Windows dialog box that has the standard 'OK' and 'Cancel' buttons. Given that Windows uses the same button text in its own dialogs is there a way for me to grab the correct strings to use on the buttons?
This way my application will have the correct strings no matter which language is being used, without me needing to localize it for lots of different languages myself. I am using C# but can happily use platform invoke to access an OS method if needed.
NOTE: Yes, I can easily localize the resources but I do not want to find and have to enter the zillion different language strings when it must be present within windows already. Please do not answer by saying localize the app!

In Visual Studio: File + Open + File, type c:\windows\system32\user32.dll. Open the String Table node and double click String Table. Scroll down to 800.
Microsoft takes a pretty no-nonsense stance against relying on these resource IDs. Given the number of programmers who've done what you're contemplating, it is however unlikely they can ever change these numbers. You'll need to P/Invoke LoadLibrary() and LoadString().
However, your ultimate downfall on this plan is Vista/Win7 Ultimate with MUI language packs. Which allows the user to switch between languages without updating the resource strings in the DLLs. Such an edition will always have English strings.

see MB_GetString which claims to do exactly this:
https://msdn.microsoft.com/en-us/library/windows/desktop/dn910915(v=vs.85).aspx
however, it seems to require runtime linkage:
http://undoc.airesoft.co.uk/user32.dll/MB_GetString.php

Well, if you use the standard MessageBox.Show() function and pass it approriate parameters it will automatically localize the yes/no/okay/cancel buttons for you.
What is more interesting is how you localize the message text.

No, there is no standard, supported way to do this. Yes, Windows does store these strings and it's (with some effort) possible to obtain them, but there is no guarantee that they'll remain in the same location and under the same identifier from version to version.
While you might not want this to be the answer, the answer is, indeed, to localize your application. If you're localizing everything else (as you'd have to, unless you just wanted OK and Cancel to be localized), I'm not sure why it would be any great effort to include localized values for OK and Cancel as well.

What type of BarCode is this?

I am starting the process of writing an application, one part of which is to decode bar codes, however I'm off to a bad start. I am no bar code expert and this is not a common bar code type, so I'm in trouble. I cannot figure out what type of bar code this is, which I have to decode.
I have looked on Wikipedia and some other sites with visual descriptions of different types of bar codes (and how to identify them), however I cannot identify it. Please note that I have tried several free bar code decoding programs and they have all failed to decode this.
So here is a picture of that bar code:
alt text http://www.shrani.si/f/2B/4p/4UCVyP72/barcode.jpg
I hope one of you can recognize it. Also if anyone has worked with this before and knows of a library that can decode them (from an image), I'd love to hear about them.
I'm very thankful for any additional pointers I can receive. Thank you.

zbar thinks it's Code 128 but the decoded string is suspiciously different than the barcode's own caption. Maybe it's a charset difference?
~/src/zebra-0.5/zebraimg$ ./zebraimg ~/src/barcode/reader/barcode.jpg
CODE-128:10657958011502540742
scanned 1 barcode symbols from 1 images in 0.04 seconds
My old copy was called zebra but the library is now called zbar. http://sourceforge.net/projects/zbar/

I don't recognize this bar code - but here are a few sites that might help you (libraries etc.) - assuming you use C# and .NET (you didn't specify in your question):
http://www.idautomation.com/csharp/
http://www.bokai.com/barcode.net.htm

It looks a bit like Code 128 but http://www.onlinebarcodereader.com/ does not recognize it as such. Maybe the image quality isn't good enough.

If you are using Java:
http://code.google.com/p/zxing/
Open Source, supports multiple types of barcodes
A list of software can be found here:
http://www.dmoz.org/Computers/Software/Bar_Code/Decoding/

IANABCE (I Am Not A Barcode Expert), but looking at the barcodes here, I'd say this looks closest to the UCC/EAN-128 symbology, character set 'C'.
Do you know what the barcode is used for? What's the application domain?