call PB DLL from C#

[Krister Olsson]

I work for a company that makes heat exchangers and I have written a PowerBasic DLL that helps our customers to select the right exchanger.
Now a new customer want an ActiveX DLL instead of a PowerBasic DLL because he thinks he will have problems to call the DLL from C# (and he knows how to use ActiveX DLLs). I have promised him to try to find the right way to "declare" and call my DLL in C# (so I do not have to write an ActiveX DLL)

In PowerBasic the subs in the DLL look like this:

 SUB Get_Calculation(B1 AS BYTE, B2 AS BYTE, HeatexIn AS DOUBLE, _
 sHeatexType AS ASCIIZ, B3 AS BYTE, B4 AS BYTE, HeatexOut AS DOUBLE)
 EXPORT

 SUB Get_Price (B1 AS BYTE, B2 AS BYTE, PriceIn AS DOUBLE, _
 sHeatexType AS ASCIIZ, B3 AS BYTE, B4 AS BYTE, PriceOut AS DOUBLE,
 sArtCode AS ASCIIZ) EXPORT

In VB6 declarations of the DLL look like this:

 Declare Sub Get_Calculation Lib "HEATEX32.DLL" Alias
 "GET_CALCULATION" _ (b1 As Byte, b2 As Byte, heatexin As Double,
 ByVal X$, _ B3 As Byte, b4 As Byte, heatexout As Double)

 Declare Sub Get_Price Lib "HEATEX32.DLL" Alias "GET_PRICE" _
 (b1 As Byte, b2 As Byte, pricein As Double, ByVal X$, _
 B3 As Byte, b4 As Byte, priceout As Double, ByVal Y$)

Does anybody know the subs should be called in C#?

Best Regards

Krister Olsson



------------------

[Brad McLane]

Try this

// using statments here...
using System;
using System.Runtime.InteropServices;


// In your public declarations part of your class

public class Myclass
{

    [DllImport("HEATEX32.DLL",SetLastError=true, CharSet=System.Runtime.InteropServices.CharSet.Ansi)]
    public static extern void Get_Calculation( 
            byte b1, byte b2, double heatexin, 
            string X, byte B3,
	    byte b4, double heatexout);
    public static extern void Get_Price(
            byte b1, byte b2, double PriceIn, 
	    string X, byte B3, Byte b4, 
            double Priceout, string Y);

 

   protected override void MyMethod()
   {

   // Declare and initialize the appropriate variables
       // Call the subs
       Get_Calculation(b1, b2 heatexin, x, B3, b4, heatexout);
       Get_Price(b1, b2, PriceIn, X, B3, b4, Priceout, Y);

   }
  }

If you want more information look in the help under DllImport statement.

Hope this helps!

- Brad

------------------




[This message has been edited by Brad McLane (edited April 22, 2004).]

[Tom Hanlin]

Well, no.

Look up "C" in the PB/Win help index for general information.

PB passes parameters BYREF by default. C/C++ passes BYVAL always,
so you will need to adjust BYREF parameters to use pointers.

PB has SUBs and FUNCTIONs. C/C++ only has functions. A function
that doesn't return a value is shown as returning "void".

C++ compilers apply "name decoration", which means that they mangle
the function names artistically, so as to reflect the nature of the
parameters passed to the function. To avoid this, you need to declare
the functions using the C convention rather than the C++ convention.

PB exports symbol names in all-caps, by default. C/C++ is case-sensitive,
so you need to match the capitalization exactly. Let me make that quite
clear: everything in C/C++ is case-sensitive, so you need to match the
capitalization exactly.

PB include files are typically named with a .inc file extension. The
C convention is to use .h.

I'll presume that the standard Windows typedefs and macros are present
in the C/C++ program, as part of an earlier #include.

So, we'll figure that you'll create a heatex32.h file, something like
this:

// HeatEx32.dll copyright (c) 2004 Krister Olsson [or whatever]
//

#ifndef HEATEX32_H     // avoid processing more than once

#define HEATEX32_H

#ifdef __cplusplus
extern "C" {
#endif


void GET_CALCULATION (BYTE * B1, BYTE * B2, double * HeatexIn,
  LPSTR sHeatexType, BYTE * B3, BYTE * B4, double * HeatexOut);

void GET_PRICE (BYTE * B1, BYTE * B2, double * PriceIn,
  LPSTR sHeatexType, BYTE * B3, BYTE * B4, double * PriceOut,
  LPSTR sArtCode);


#ifdef __cplusplus
}
#endif

#endif  // #ifndef HEATEX32_H

The way these routines are called will depend on whether the customer
is using LoadLibrary. They may find it more convenient to use an import
library, which would let them make the calls without needing LoadLibrary
(the way you're familiar with in PowerBASIC)-- but, creating an import
library will take a little more work on your end. Try a forum search
for "import library" for more information.

------------------
Tom Hanlin
PowerBASIC Staff

[Brad McLane]

Tom,

The question was about interfacing with c-sharp, not C plus plus.

The way I described it is how you call "unmanaged" code from .NET C#.

- Brad

------------------


[This message has been edited by Brad McLane (edited April 27, 2004).]

[Tom Hanlin]

Good point. I haven't tried making .dll declarations for C#. I expect
that BYVAL vs BYREF and case sensitivity are still important, though.

------------------
Tom Hanlin
PowerBASIC Staff