Array of strings to old DLL? - C# Discussion Boards

2-Sep-02 5:02

Im not really sure what a union in C++ does, it appears to join 2 variables into one, hence the commented dmNup. Can anyone C++ person please explain this in C# terms?

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Paul Riley2-Sep-02 5:57

Paul Riley

2-Sep-02 5:57

A union uses the same piece of memory for two different variables.

For example

struct INTCHARS
{
    char hi;
    char midhi;
    char midlo;
    char lo;
};


union FOURBYTES
{
    INTCHARS ch;
    int i;
};


FOURBYTES four;
four.ch.hi = 1;
four.ch.midhi = 1;
four.ch.midlo = 1;
four.ch.lo = 1;
four.i = 0;

Now each part of four.ch is 0.

Going back a while since I used one of these. Smile | :)

Paul

leppie2-Sep-02 6:12

2-Sep-02 6:12

Thx,

From what i can see is that unions are class like structures in a struct or class allowing easy retriaval/setting of inner variables. I have been using SequintialLayout classes todo this. Im not sure if we are talking the same thing, but I guess thats why the are not included in C#.

Cheers Smile | :)

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Paul Riley2-Sep-02 8:00

Paul Riley

2-Sep-02 8:00

The big difference between a union and a struct is that changing one inner variable in a union will change all of them because they share the same space in memory.

As C++ came into play, unions became less useful, classes and pointers could be used to the same effect.

When PCs with more than 50 bytes of spare memory came out, unions again lost some usefulness. Wink | ;)

Likewise properties haven't done unions any favours, you can now reference the same variable in different ways through get/set properties.

So I wouldn't be surprised if C# didn't have an equivalent, though there are times when it wouldn't go amiss.

Paul

Paul Ingles2-Sep-02 7:52

Paul Ingles

2-Sep-02 7:52

From what I understand (I also was looking into unions recently -- trying to DllImport DnsQuery_A) a union is a UDT which allows for one datatype or another, so if you specify it with a String or Int32 it would let the value be one of the two. At least that was what I took it to mean Smile | :)

I'm not aware of a native C# equivalent but would be glad to know of one!

--
Paul
"I need the secure packaging of Jockeys. My boys need a house!"
- Kramer, in "The Chinese Woman" episode of Seinfeld

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James T. Johnson2-Sep-02 9:38

James T. Johnson

2-Sep-02 9:38

As others have said a union just uses the same memory space to hold each of the types (thus only allowing one of them to be used at a time).

Typically when you are dealing with a union you have to break it out into its own datatype so that you can properly use it in code. Otherwise you could be having to use the same variable for two vastly different things such as a pointer to a string and a byte which will be hard to do when dealing with a single member.

To create a union in C#:

[StructLayout(LayoutKind.Explicit)]
public struct myUnion
{
  [FieldOffset(0)] string FieldA;
  [FieldOffset(0)] bool FieldB;
  [FieldOffset(4)] int FieldC;
  [FieldOffset(4)] long FieldD;
  [FieldOffset(12)] int Foo;
  [FieldOffset(12)] char Bar;
  [FieldOffset(12)] float Baz;
}

The numbers used will position where in memory each field will be placed, using the technique you can also create multiple unions as I did above (FieldA and FieldB; FieldC and FieldD; and Foo, Bar, and Baz; are all unions, where only one of the members can be used).

Hope that makes sense.

James
"And we are all men; apart from the females." - Colin Davies

Array of strings to old DLL?

Paul Riley2-Sep-02 9:52

Paul Riley

2-Sep-02 9:52

That is very cool, James, nice one! Cool | :cool:

Paul

EdgarBM1-Sep-02 23:25

1-Sep-02 23:25

Hi,
I have an old DLL developped on VC++ 6.0. It was designed to work with VB and VC code. The problem always has been two special parameters which where an array of vaules. One was an array of doubles and the other an array of strings.
It was hard, but I solved it using the SAFEARRAY structure, this way:
Method (..., SAFEARRAY FAR *doubleArray, SAFEARRAY FAR *stringArray, ...)

-> To call the library from VB code I only should do:

Dim dbArray() as double<br />
Dim stArray() as string<br />
Redim dbArray(5)<br />
dbArray(0) = 3.4<br />
...<br />
'and so to strings

->To call it from VC it was more difficult:

char sMatriz[1][256/*128x2, chars doubled!*/];<br />
strcpy (sMatriz[0], "H E L L O "); //the space represents the NULL between the string characters due to compatibility with COM ; not for doubles array<br />
LPSAFEARRAY sS = new struct tagSAFEARRAY;<br />
sS->pvData=sMatriz;<br />
sS->rgsabound->cElements = 1;<br />
//...and I passed the reference of the LPSAFEARRAY: <br />
Method (..., &sD, &sS, ...)

THE PROBLEM:
---------------------
Now I want this library to be used on C# or VB.NET, but I don't know the way to instantiate and pass those parameters. Any chance I get an exception like this:

System.NullReferenceException<br />
Exception Details: Object reference not set to an instance of an object.

I pass those parameters like:

string[] sA = new string[5]; double[] dA = new double[5];<br />
Method (..., dA, sA,...)

...and if I modify the library taking out those params (ignoring them), everything works fine.

Does anyone knew how can I solve this problem? Is there any special way to pass those parameters?, anything before changing the library? I really need those params in the library!

Thank you in advance, (thanks if you read all the text!)
Edgar

Edgar Berengena Moreno
Software Engineer
Appeyron Research

Stephane Rodriguez.1-Sep-02 23:38

1-Sep-02 23:38

A SAFEARRAY in C++ like this :

HRESULT GetItems([in] BSTR bstrLocation, [out] SAFEARRAY(VARIANT)* pItems);

is marshalled back and forth with C# declaration like this in your interface :

[ComImport]
[Guid("73EB4AF8-BE9C-4b49-B3A4-24F4FF657B26")]
public interface IMyStorage  
{
  [DispId(2)]
  void GetItems( [In, MarshalAs( UnmanagedType.BStr )] String bstrLocation, 
         [Out, MarshalAs( UnmanagedType.SafeArray, SafeArraySubType = VarEnum.VT_VARIANT )] out Object[] Items );

...
}

Further details.

And I swallow a small raisin.

EdgarBM2-Sep-02 1:14

2-Sep-02 1:14

Thanks,

...but I can't improve anything with this! I'm trying to pass an Object[] to the library but I'm still getting the same exception.

Is there anymore information or runnig sample which solves this problem?, does anyone know it??

Thank you again,
Edgar

Edgar Berengena Moreno
Software Engineer
Appeyron Research

Stephane Rodriguez.2-Sep-02 1:33

2-Sep-02 1:33

Can you try the following code :

string[] MyString = {"Hello", "and", "welcome", "to", "my" , "world!"};

I am not sure the exception you have is a marshalling issue.

And I swallow a small raisin.

EdgarBM2-Sep-02 1:52

2-Sep-02 1:52

Thank you, Stephane, but It doesn't work. I always thought this was the correct solution, but it gaves me the System.NullReferenceException exception.

If you have any other idea, please let me know.
Thank you,
Edgar

Edgar Berengena Moreno
Software Engineer
Appeyron Research

leppie2-Sep-02 1:50

2-Sep-02 1:50

Hi maybe I can help.

1. Create arrays, like normal
2. Before calling function, foreach array, allocate mem, copy array to pointer and pass the pointer.
3. when the array returns copy the pointer back to the array.

For example: From MDSN

// array ByRef
int[] array2 = new int[ 10 ];
int size = array2.Length;

IntPtr buffer = Marshal.AllocCoTaskMem( Marshal.SizeOf( size )
   * array2.Length ); // or Marshal.AllocHGlobal (COM or not)
Marshal.Copy( array2, 0, buffer, array2.Length );

int sum2 = LibWrap.TestRefArrayOfInts( ref buffer, ref size ); // replace this with your function replaceing arrays with IntPtr

if( size > 0 )
{
   int[] arrayRes = new int[ size ];
   Marshal.Copy( buffer, arrayRes, 0, size );
   Marshal.FreeCoTaskMem( buffer ); //or Marshal.FreeHGlobal
}

Now just do this to each array. Unfortunately u dont give the whole function as defined in a header file, so I cant gaurentee this will work, but it works in my case when normal marshalling wouldnt work Smile | :)

Hope this helps

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EdgarBM2-Sep-02 2:10

2-Sep-02 2:10

Thanks for your reply, Leppie.

The only problem is that I'm working with string arrays too, so the Copy method of Marshall can't be applied.
I can't say if it works or doesn't work because I need to manage the string array too so keeps receiving the exception...although it seems to work for the double[] (maybe I hope)!!

Any idea for the string array?

PS: the unmanaged DLL parameters (VC++ 6.0 DLL) are defined as
SAFEARRAY FAR *doubleArray, SAFEARRAY FAR *stringArray
...these are the conflicting ones.

Thank you again,
Edgar

Edgar Berengena Moreno
Software Engineer
Appeyron Research

leppie2-Sep-02 2:33

2-Sep-02 2:33

Hi try this, glad to see double[] works Smile | :)

Try this:

ArrayList tags = new ArrayList();
do 
{
  string tag = Marshal.PtrToStringUni(ptag); 
  // ptag is pointer to string[], make sure about unicode/ansi, i assume unicode
  if (tag == "") break;
  else 
  {
    tags.Add(tag);
    ptag = new IntPtr(ptag.ToInt32() + Marshal.SizeOf(tag));
  }
}
while(true);

This reversse can be done if u need to "feed" the function with the string[].

Hope this works

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EdgarBM2-Sep-02 21:44

2-Sep-02 21:44

Hi,
I'm trying your second code but I'm having problems and I don't know if I'm doing it quite well. That's what I'm trying now:

For the double[]:

<br />
IntPtr buffer = Marshal.AllocCoTaskMem( Marshal.SizeOf( cantidad ) * sVN.Length); // or Marshal.AllocHGlobal (COM or not)      <br />
Marshal.Copy( sVN, 0, buffer, sVN.Length );<br />

...and for the string[]:

<br />
IntPtr ptag = new IntPtr ();<br />
ptag = Marshal.StringToHGlobalAnsi ("maybe...");<br />
ArrayList tags = new ArrayList();<br />
do <br />
{<br />
	string tag = Marshal.PtrToStringAnsi (ptag); //PtrToStringUni (ptag);    // ptag is pointer to string[], make sure about unicode/ansi, i assume unicode  <br />
	if (tag == "") break;  <br />
	else   <br />
	{    <br />
		tags.Add(tag);    <br />
		ptag = new IntPtr(ptag.ToInt32() + <br />
		Marshal.SizeOf(Marshal.StringToHGlobalAnsi (tag)));  <br />
	}<br />
}while(true);

And I define the DLL Function like:
Method (..., ref IntPtr sbufN, ArrayList sbufC, ...);

What am I doing wrong?

Thank you again for your dedication,
Edgar

__________________________________________
Edgar Berengena Moreno
Software Engineer
Appeyron Research

leppie3-Sep-02 2:19

How to do a virtual keyboard in c# ?

3-Sep-02 2:19

HoHa what a mess Smile | :)

Method (..., IntPtr sbufN, IntPtr sbufC, ...);

string[] strarr = new string[]{"one","two","three","four"};
IntPtr firstpointer;
int counter = 0;
foreach (string str in strarr)
{
  IntPtr ptr = Marshal.StringToHGlobalUni(str);
  if (counter++ == 0) firstpointer = ptr;
}

Method(..., IntPtr sbufN, firstpointer,...);

for (int i = 0; i < strarr.Length; i++)
{
  strarr[i] = Marshal.PtrToStringUni(firstpointer);
  firstpointer = new IntPtr(firstpointer.ToInt32() + Marshal.SizeOf(strarr[i]));
}

Ok try that Smile | :)

Like I said it is very important to know whether the function will need values from the string array when passing it to the function. What is the function to do / return with the string[] ???

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AlbertoFujimori1-Sep-02 21:34

AlbertoFujimori

1-Sep-02 21:34

A virtual keyboard is a form with keys (buttons) that act as keyboard on touch-screens (for example)
Thanks
Stephane

Re: How to do a virtual keyboard in c# ?

Stephane Rodriguez.2-Sep-02 0:01

BringToFront changes index

2-Sep-02 0:01

There is the UI part and there is virtual key localisation.

About UI, the simplest is to add KeyPress or KeyUp event handlers to your form, so it hooks every key. Then e.KeyCode, or e.Key depending on the handler will return the virtual key code or ANSI code.

Add an imagelist to buttons. And swap images along in event handlers. That will do highlighting.

About localisation, well that's a job that takes time because you'll have to provide cultures keyboard schemes such like AZERTY in French. Which means you have to provide a different set of positioned buttons.
You may of course limit yourself with QWERTY, but ... Unsure | :~

My 0.5 cent,

And I swallow a small raisin.

James McCutcheon1-Sep-02 20:32

James McCutcheon

1-Sep-02 20:32

Just thought I would make people aware of something I noticed, ok it took me a while to work out why and I had to tell somebody ...

I just noticed that if you use the method BringToFront for a label control the index for the control moves.

- James

Graphic engine for .NET anyone?

Alastair Stell1-Sep-02 16:01

Alastair Stell

1-Sep-02 16:01

I would like to build an application which incoporates 2D graphics. Macromedia / Shockwave jumps to mind in terms of the graphic content I would like to aim for.

I've considered using DirectX but this seems like overkill, and besides there is presently no C# interface to DirectX and I would need to program in C++ to use the SDK (correct me if this statement is wrong, please!).

I'm not out to build a web enabled program and I don't need cross-platform portability.

Does anyone know if there is a 2D graphic engine / library out there which works with .NET? (prefereably C# but C++ is okay).

Thanks in advance!

Only change is constant

David Stone1-Sep-02 17:58

David Stone

1-Sep-02 17:58

Have you looked into using the System.Drawing.2D namespace? That is .NET's interface to GDI+. If 2D is all you're going to do, you may just want to use that.

David Stone

But Clinton wasn't a predictable, boring, aging, lying, eloquent, maintainer-of-the-status-quo. He was a predictable, boring-but-trying-to-look-hip, aging-and-fat-but-seemingly-oblivious-to-it, lying-but-in-sadly-blatant-ways, not-eloquent-but-trying-to-make-up-for-it-by-talking-even-more, bringer-in-of-scary-and-potentially-dangerous-new-policies. And there was also Al Gore. It just wasn't *right*.

Shog⁹

Rickard Andersson²⁰1-Sep-02 20:47

Rickard Andersson²⁰

1-Sep-02 20:47

Alastair Stell wrote:
I've considered using DirectX but this seems like overkill, and besides there is presently no C# interface to DirectX and I would need to program in C++ to use the SDK (correct me if this statement is wrong, please!).

I've seen on websites that people has done games in C# using DirectX.... if they're dreaming or what, I don't know! Smile | :)

But I'm pretty sure it is a DirectX for C#!

Rickard Andersson@Suza Computing
C# and C++ programmer from SWEDEN!
UIN: 50302279
E-Mail: nikado@pc.nu
Speciality: I love C#, ASP.NET and C++!

Stephane Rodriguez.1-Sep-02 21:20

1-Sep-02 21:20

Many developers have made fine games using VB, thus using C# should be more or less the same.

Of course there are bottlenecks. For instance a .Net application needs at least 4 seconds before it starts (time required for the CLR to compile IL code into assembly code). So don't expect much about time response.

You have at least two options :
- use plenty of ActiveX, for instance the one from Macromedia

- use the System.Drawing assembly, even though you'll end up as with Java 1.0 back 4 years ago : in other words, 1. anything you do requires you to manage your own double buffers, and optimized drawing so the screen does not flicker. 2. the object model is primitive : for instance you cannot draw an arrow. 3. Transparency API ? play with caution, some features will work only on W2K/XP systems. 4. DirectX ? never assume that what works fine on your computer will work on someoneelse's computer. That's the conclusion I made after 2 years of DirectX struggle (where the so-called hardware abstraction at the basis of the whole stuff, is in fact a complete lie). Besides that, manipulating all interface versions will require a full-time job just for it. Cry | :((

And I swallow a small raisin.

leppie2-Sep-02 5:24