DllImport problem

[mrssuper]

Hey All,


How do I declare a following types:

 char** 
 unsigned char**

in C# DllImport function?

C++ function signature

-----------------------------------------------------------------------------------------------------------
extern "C" __declspec(dllimport) int Get
(int*     pEnrollNumber,                                                          
 char** EnrollNames,                                                          
 int*     EnrollIDs,                                                         
 unsigned char** EnrollTemplates,
 int* EnrollTemplateSizes,                                                       
 int Delay);
-----------------------------------------------------------------------------------------------------------

I tried to use an IntPtr instead of both char** and unsigned char**,
but it throws an AccessViolation Exception.

If I declare a char** (for char**) and byte** (instead of unsigned char**) I still get the same exception but it seems to me the problem in this case is because of
parameters i pass to the function(i'm not quite sure how to declare it..)



C# declarations i tried:

 [DllImport("TLib.dll")]
        private static extern int EnrollGet
( ref int pEnrollNumber, char** EnrollNames,
  ref int EnrollIDs, 
  byte** EnrollTemplates,
  ref int EnrollTemplateSizes,
  int Delay);
 
or

 [DllImport("TLib.dll")]
        private static extern int EnrollGet
( ref int pEnrollNumber, 
 out IntPtr EnrollNames,
 ref int EnrollIDs, 
 out IntPtr EnrollTemplates,
 ref int EnrollTemplateSizes,
int Delay);

Can anyone please help me to solve this issue?

Thanks in advance

[mrssuper]

I finally solved the problem.

I left the declaration as it is in C++:

[DllImport("TLib .dll")]
public static extern int Get( int* pEnrollNumber,c har** EnrollNames,int * EnrollIDs,
byte** EnrollTemplates ,int* EnrollTemplateS izes, int Delay);

Turns out that all integers point also to arrays so I created the following class:


unsafe class CUser
{
public int m_Number;
public int m_Index;
public char*[] m_Names;
public int[] m_IDs;
public int[] m_TemplateSizes ;
public byte*[] m_Templates;

public CUser()
{

// 1000 = db size

m_Number = 0;
m_Index = 0;
m_Names = new char*[1000];
m_IDs = new int[1000];
m_TemplateSizes = new int[1000];
m_Templates = new byte*[1000];

for (int i = 0; i < 1000; ++i)
{
m_Names[i] = (char*)Memory.A lloc(64);
m_Templates[i] = (byte*)Memory.A lloc(1000);
}
}

~CUser()
{


for (int i = 0; i < MAX_USER_ENTRIE S; ++i)
{
Memory.Free(m_T emplates[i]);
}
}
}

The trick is to allocate the memory for both the array of strings and bytes and pass a correct parameters which I didn't before.
I did it using the microsoft sample of dinamic Memory allocation.
The Class found in: http://msdn.microsoft.com/en-us/libr...86(VS.71).aspx


The function call:




unsafe
{

CUser users = new CUser();




fixed (int* num = &users.m_Number , ids = &users.m_IDs[0], sizes = &users.m_Templa teSizes[0])
{
fixed (byte** temps = &(users.m_Templ ates[0]))
{
fixed (char** names = &(users.m_Na mes[0]))
{
int result = Helper.Get(num, names, ids, temps, sizes);
}
}
}
}

Maybe it a little bit difficult, but it works..