How to pass an array between a Visual Basic .NET or Visual Basic 2005 application and a Visual C++ .NET or Visual C++ 2005 function (841293)

SUMMARY

• Microsoft .NET Framework assembly
• Win32 DLL
• Component Object Model (COM) DLL

INTRODUCTION

Requirements

• Microsoft Visual Basic .NET or Microsoft Visual Basic 2005 programming
• Microsoft Visual C++ .NET or Microsoft Visual C++2005 programming
• Microsoft Active Template Library (ATL) programming

• Microsoft Visual Studio .NET or Microsoft Visual Studio 2005
• Microsoft Visual Basic .NET or Microsoft Visual Basic 2005
• Microsoft Visual C++ .NET or Microsoft Visual C++ 2005
• Microsoft .NET Framework

Create a Visual Basic .NET or Visual Basic 2005 application

1. Start Microsoft Visual Studio .NET or Microsoft Visual Studio 2005.
2. On the File menu, point to New, and then click Project. The New Project dialog box appears.
3. Under Project Types, click Visual Basic Projects.
   
   Note In Visual Studio 2005, click Visual Basic under Project Types.
4. Under Templates, click Console Application.
5. In the Name box, type MyVBApp, and then click OK.

Pass an array to a function in a .NET Framework assembly

Create an assembly by using Visual C++ .NET or Visual C++ 2005

1. Start Visual Studio .NET or Visual Studio 2005.
2. On the File menu, point to New, and then click Project. The New Project dialog box appears.
3. Under Project Types, click Visual C++ Projects.
   
   Note In Visual Studio 2005, click Visual C++ under Project Types.
4. Do one of the following, depending on the version of Visual C++ .NET or Visual C++ 2005 that you are using:
   • If you are using Microsoft Visual C++ .NET 2003, click Class Library (.NET) under Templates.
   • If you are using Microsoft Visual C++ .NET 2002, click Managed C++ Class Library under Templates.
   • If you are using Microsoft Visual C++ 2005, click Class Library under Templates.
5. In the Name box, type MyCDll, and then click OK.

Write a Visual C++ .NET function that expects an array

1. In Solution Explorer, double-click MyCDll.h under Header Files.
2. Add the following code to the Class1 class:

   /*========================================================
   SearchNum_Assembly is a function that searches for a number 
   in the array. If the specified number is present,
   the function returns the position of the element in the array.
   ==========================================================*/
   public:
   int SearchNum_Assembly(int numArr __gc[], int searchnum)
   {
      int i,value=0;
      for (i=0;i<numArr->Count;i++)
      {    
         if (searchnum==numArr[i])	
         {
             value=i+1;
             break;
         }
      }
      //Return the position of the number in the array.
      return value;
   }
   

3. On the Build menu, click Build MyCDll to create the MyCDll.dll file. By default, MyCDll.dll file is created in the Debug folder that is located in your project folder.
4. On the File menu, click Exit to close the MyCDll project.

Call the function in the .NET Framework assembly

1. Switch to the Visual Basic .NET or Visual Basic 2005 project.
2. In Solution Explorer, right-click MyVBApp, and then click Add Reference. The Add Reference dialog box appears.
3. In the Add Reference dialog box, click the .NET tab, and then click Browse. The Select Component dialog box appears.
4. In the Select Component dialog box, locate the MyCDll folder on your computer. Double-click the MyCDll folder, and then double-click the Debug folder.
5. In the Select Component dialog box, click MyCDll.dll, and then click Open.
6. In the Add Reference dialog box, click OK.
7. Add the following code to the Main procedure:

   'Declare an integer array, and then initialize the array.
   Dim nums() As Integer = {1, 2, 3, 4, 5, 6}
   Dim result, searchNum As Integer
   searchNum = InputBox("Enter the number to be searched:")
   Dim obj As New MyCDll.Class1
   'Pass the elements of the array to the SearchNum_Assembly function
   'in the MyCDll assembly.
   result = obj.SearchNum_Assembly(nums, searchNum)
   Console.WriteLine("RESULT WHEN THE ARRAY IS PASSED TO A FUNCTION IN Visual C++ .NET ASSEMBLY:")
   If result <> 0 Then
       Console.WriteLine("The number is present and the position of the number is:" & result)
   Else
       Console.WriteLine("The number is not present.")
   End If
   Console.ReadLine()
   

Pass an array to a function in a Win32 DLL

int __declspec (dllexport) __stdcall SearchNum_Win32( int *numArr, int count, int searchnum);

Private Declare Function SearchNum_Win32 Lib "<Full Path of DLL>" _
       (ByRef nums As Integer, ByVal count As Integer, ByVal searchNum As Integer) As Integer

Create a Win32 DLL by using Visual C++ .NET

1. Start Visual Studio .NET or Visual Studio 2005.
2. On the File menu, point to New, and then click Project. The New Project dialog box appears.
3. Under the Project Types section, click Visual C++ Projects.
   
   Note In Visual Studio 2005, click Visual C++ under Project Types.
4. Under the Templates section, click Win32 Project.
5. In the Name box, type MyWinDll.
6. In the Location box, type C:\WinDll, and then click OK. The Win32 Application Wizard - MyWinDll wizard starts.
7. On the Welcome to the Win32 Application Wizard page, click Application Settings.
8. On the Application Settings page, click DLL, and then click Finish.

Write a Visual C++ .NET or Visual C++ 2005 function that expects a pointer to an array

1. In Solution Explorer, right-click Header Files, point to Add, and then click Add New Item. The Add New Item - MyWinDll dialog box appears.
2. Under Templates, click Header File (.h).
3. In the Name box, type MyWinDll, and then click Open. The MyWinDll.h file opens in code view.
4. Add the following code to the MyWinDll.h file:

   #include <windows.h>
   int __declspec (dllexport) __stdcall SearchNum_Win32(int 
   *numArr, int count, int searchnum);
   

5. In Solution Explorer, right-click MyWinDll.cpp, and then click Open. The MyWinDll.cpp file opens in code view.
6. Add the following code at the end of the MyWinDll.cpp file:

    #include "MyWinDll.h"
   
    /*========================================================
      SearchNum_Win32 is a function that searches for a specified number 
      in the array that is passed as a pointer. If the specified number is present,
      the function returns the position of the element in the array.
      ==========================================================*/ 
   
   int __declspec (dllexport) __stdcall SearchNum_Win32(
    int *numArr, // The array's pointer
    int count, // The number of elements in the array 
    int searchnum)// The number to be searched
    {
   
      int i,value=0;
      for (i=0;i<count;i++)
      {    
         if (searchnum==numArr[i])	
         {
             value=i+1;
             break;
         }
      }
      //Return the position of the number in the array.
      return value;
    }
   

7. In Solution Explorer, right-click Source Files, point to Add, and then click Add New Item. The Add New Item - MyWinDll dialog box appears.
8. Do one of the following, depending on the version of Visual C++ .NET that you are using:
   • If you are using Visual C++ .NET 2003, click Module-Definition File (.def) under Templates.
   • If you are using Visual C++ .NET 2002, click DEF File (.def) under Templates.
9. In the Name box, type MyWinDll, and then click Open. The MyWinDll.def file opens in code view.
10. Add the following code at the end of the MyWinDll.def file:

    EXPORTS 
    SearchNum_Win32

11. On the Build menu, click Build MyWinDll.
12. On the File menu, click Exit to close the MyWinDll project.

Call the function in the Win32 DLL

1. Switch to the Visual Basic .NET or Visual Basic 2005 project.
2. Add the following code before the Main procedure in the Module1 module:

   Private Declare Function SearchNum_Win32 Lib "C:\WinDll\MyWinDll\Debug\MyWinDll.dll" _
          (ByRef nums As Integer, ByVal count As Integer, ByVal searchNum As Integer) As Integer
   

3. Locate the following code:

   End Sub

4. Add the following code to the Main procedure. Add this code before the code that you located in step 3:

   'Pass the first element of the integer array to the SearchNum_Win32 function
   'in the MyWinDll Win32 DLL.
   Dim presult As Integer
   presult = SearchNum_Win32(nums(0), UBound(nums) + 1, searchNum)
   Console.WriteLine("RESULT WHEN THE FIRST ELEMENT OF THE ARRAY IS PASSED TO A FUNCTION IN WIN32 DLL:")
   If presult <> 0 Then
       Console.WriteLine("The number is present and the position of the number is:" & presult)
   Else
       Console.WriteLine("The number is not present.")
   End If
   Console.ReadLine()
   

Pass an array to a function in a COM DLL

Create a COM DLL by using Visual C++ .NET

1. Start Visual Studio .NET or Viusal Studio 2005.
2. On the File menu, point to New, and then click Project. The New Project dialog box appears.
3. Under Project Types, click Visual C++ Projects.
   
   Note In Visual Studio 2005, click Visual C++ under Project Types.
4. Under Templates, click ATL Project.
5. In the Name box, type MyAtlDll, and then click OK. The ATL Project Wizard - MyAtlDll starts.
6. On the Welcome to the ATL Project Wizard page, click Application Settings.
7. On the Application Settings page, click Dynamic-link library (DLL), click to clear the Attributed check box, and then click Finish.

Write a Visual C++ .NET or Visual C++ 2005 function that expects a SAFEARRAY

struct SAFEARRAY
 {
      WORD cDims; // The number of dimensions
      WORD fFeatures; // The bitfield that indicates the attributes of a specific
                      // array
      DWORD cbElements; // The size of an element of the array
      DWORD cLocks; // The lock counter
      Void * pvData; // The pointer to the array's elements (use only if the value
                     // of cLocks is greater than 0)
      SAFEARRAYBOUND rgsabound[1]; // The structure that contains information for
                                   // each dimension
 };

1. In Solution Explorer, right-click Source Files, point to Add, and then click Add Class. The Add Class - MyAtlDll dialog box appears.
2. Under Templates, double-click ATL Simple Object. The ATL Simple Object Wizard - MyAtlDll starts.
3. On the Welcome to the ATL Simple Object Wizard page, type MyClass in the Short name box, and then click Options.
4. On the Options page, verify that:
   • Threading model is set to Apartment.
   • Aggregation is set to Yes.
   • Interface is set to Dual.
   Click Finish.
5. On the View menu, click Class View.
6. In class view, expand MyAtlDll, right-click IMyClass, point to Add, and then click Add Method. The Add Method Wizard - MyAtlDll starts.
7. On the Welcome to the Add Method Wizard page, type SearchNum_Com in the Method name box.
8. In the Parameter type box, type SAFEARRAY*.
9. In the Parameter name box, type numArr, and then click Add.
10. Repeat steps 8 and 9 for the following values:

    Parameter type	Parameter name
    int	searchnum
    int*	result

11. On the Welcome to the Add Method Wizard page, click Finish.
12. On the View menu, click Solution Explorer.
13. In Solution Explorer, right-click MyAtlDll.idl, and then click Open. The MyAtlDll.idl file opens in code view.
14. Locate the following code:

    [id(1), helpstring("method SearchNum_Com")] HRESULT SearchNum_Com(SAFEARRAY* numArr, int searchnum, int* result);

15. Replace the code that you located in step 14 with the following code:

    [id(1), helpstring("method SearchNum_Com")] HRESULT SearchNum_Com(SAFEARRAY(int) numArr, int searchnum, int* result);

16. In Solution Explorer, right-click MyClass.cpp, and then click Open. The MyClass.cpp file opens in code view.
17. Replace the existing code in the SearchNum_Com function with the following code:

    /*========================================================
    SearchNum_Com is a function that searches for a specified number 
    in the array that is passed from a Visual Basic .NET application. 
    The variable "result" is passed by reference. This variable holds 
    the results of the search. If the specified number is present,
    the function updates the variable "result" to hold the position 
    of the number in the array.
    ==========================================================*/
    int i,arrSize;
    *result=0;
    int* arrData;
    //Get the number of elements in the array.
    arrSize=numArr->cbElements;
    //Get the elements in the array.
    arrData=(int*)(numArr)->pvData;
    for (i=0;i<arrSize;i++)
    {    
       if (searchnum==arrData[i])	
          
          {
              *result=i+1;
              break;
          }
    }
    return S_OK;

18. On the Build menu, click Build MyAtlDll.
19. On the File menu, click Exit to close the MyAtlDll project.

Call the function in the COM DLL

1. Switch to the Visual Basic .NET or Visual Basic 2005 project.
2. In Solution Explorer, right-click MyVBApp, and then click Add Reference. The Add Reference dialog box appears.
3. In the Add Reference dialog box, click the COM tab, and then click Browse. The Select Component dialog box appears.
4. In the Select Component dialog box, locate the MyAtlDll folder on your computer. Double-click MyAtlDll, and then double-click Debug.
5. In the Select Component dialog box, click MyAtlDll.dll, and then click Open.
6. In the Add Reference dialog box, click OK.
7. Locate the following code:

   End Sub

8. Add the following code to the Main procedure. Add this code before the code that you located in step 7:

   Dim Atlobj As New MyAtlDllLib.MyClassClass
   'Pass the integer array to the SearchNum_Com function in
   'the COM DLL.
   Dim cres As Integer
   Atlobj.SearchNum_Com(nums, searchnum, cres)
   Console.WriteLine("RESULT WHEN THE ARRAY IS PASSED TO A FUNCTION IN THE COM DLL:")
   If cres <> 0 Then
        Console.WriteLine("The number is present and the position of the number is:" & cres)
   Else
        Console.WriteLine("The number is not present.")
   End If
   Console.ReadLine()
   

Verify that your project works

1. On the Build menu, click Build Solution.
2. On the Debug menu, click Start.