Call VC++ dll in C# Application

Question

HI,

  we are using one c++ dll to read data from Hardware. Following is the function defination from C++ dll.

  LRESULT CALLBACK MT_Read_Holding_Reg(long llSocketHandle,UCHAR lucDevID,USHORT lunAddress,USHORT lunQuantity, USHORT* lunHLData);

   To Call this from C# I have written following code:

  
   [DllImport("MT_TCP_Read.dll", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
   public static extern int MT_Read_Input_Reg(int llSocketHandle, byte lucDevID, short lunAddress, short lunQuantity, ref short lunHLData);

and while calling this function I have writtten following code:
  short[] arr_hg = new short[3];
  int ret = -1;
  ret = MT_Read_Coils(handle, 1, 100, 3, ref arr_coils[0]);

  This function return no data where as same dll used in VB6 return correct data.

  Is there any problem in above code.

  Any help appreciated.

Regards,
 
 Vikram