COM in C#

COM in C#

• Tim Cartwright

  In C#, you add a reference to your com component - just go to the solution explorer, and right click on references/add reference, then click the COM tab and look for what you want to add.

  
  
  

• beregen

  awesome, that works

  I have one more question, now do I have to make a COM component in C# or I can directly call the stuff and should work for me......

  This was the code from C++.....If you can let me know how can I call the Functions.....

  #include "stdafx.h"
  #include "sha/sha.h"
  #import "BBDevMgr.exe" no_namespace named_guids
  #include <conio.h>

  enum{ READ_EVENT, CLOSE_EVENT, NUM_EVENTS};

  //using the GCF framework on the device, the length of the inbound data is prepended to the binary stream
  // therefore, use this struct to decode the data
  //HOWEVER, in the case of the lowlevel data (net.rim.device.api.system.USBPort), the length bytes are NOT prepended
  typedef struct {
  unsigned short length;
  unsigned char data[256];
  } DEVICE_DATA;

  static const int HEADERSIZE = sizeof(unsigned short);

  static char const * const PC_HELLO = "Hello from PC";
  static char const * const PC_GOODBYE = "Goodbye from PC";
  static char const * const DEVICE_HELLO = "Hello from Device";
  static char const * const DEVICE_GOODBYE = "Goodbye from Device";
  #define CHANNEL L"RIM_USBClient"
  /**
  * The simple usb client. This opens a raw connection to the device, it is expected that an application is waiting on the device to
  * interact with this desktop process
  */
  class USBClient:
  public IChannelEvents //implements the ICHannelEvents interface in order to receive notifications on the connection to the device
  {
  public:
  USBClient()
  {
  }

  ~USBClient()
  {}

  public:

  int run()
  {

  //create some events for listening for notifications from the device
  _events[READ_EVENT] = CreateEvent(NULL, FALSE, FALSE, NULL); //unnamed
  _events[CLOSE_EVENT] = CreateEvent(NULL, TRUE, FALSE, NULL); //unnamed
  if( _events[READ_EVENT] == INVALID_HANDLE_VALUE || _events[CLOSE_EVENT] == INVALID_HANDLE_VALUE ) {
  return false;
  }

  try {
  CoInitializeEx(NULL, COINIT_MULTITHREADED);

  //grab an instance of the main proxy object: IDeviceManager
  IDeviceManagerPtr deviceManager; //(__uuidof(IDeviceManager));
  deviceManager.CreateInstance(CLSID_DeviceManager);

  //get the list of attached devices
  IDevicesPtr devices = deviceManager->Devices;

  //query the count of attached devices
  if ( devices->Count > 0 )
  {
  IDevicePtr device = devices->Item(0); //get the first

  //get the properties for the attached device
  IDevicePropertiesPtr properties = device->Properties;
  long count = properties->Count;
  for (long i = 0; i < count; ++i)
  {
  IDevicePropertyPtr property = properties->Item; //(_variant_t(i));

  char name[256];
  memset( name, 0, sizeof( name ) );
  WideCharToMultiByte( CP_ACP, 0, property->Name, SysStringLen( property->Name ),
  name, sizeof( name ), NULL, NULL );

  printf("Name: %s\n",
  name);

  _variant_t var(property->Value);
  if ( strcmp("BBPIN", name) == 0 )
  {
  long pin = (long)(var);
  printf("Value: 0x%x\n", pin);
  }
  else
  {
  printf("Value: %s\n",
  (char*)((_bstr_t)var));
  }

  }

  //open a channel and exchange some data
  printf("");
  printf("Opening Channel: %s\n", CHANNEL);
  _channel = device->OpenChannel(CHANNEL, this);

  char buffer[258];
  char * pString = NULL;

  long len = 0;
  strcpy(buffer, PC_HELLO);

  Send(buffer);

  if ( NULL != (pString = (ReadVariableProtocol(DEVICE_HELLO, buffer, sizeof(buffer), len )) ))
  {
  if ( strncmp(pString, DEVICE_HELLO, len) != 0 )
  {
  printf("Failed to receive proper string from device\n");
  }
  else
  {
  strcpy(buffer, PC_GOODBYE);
  Send(buffer);

  if ( NULL != (pString = (ReadVariableProtocol(DEVICE_GOODBYE, buffer, sizeof(buffer), len))))
  {
  if ( strncmp(pString, DEVICE_GOODBYE, len) != 0 )
  {
  printf("Failed to receive proper string from device\n");
  }
  printf("Success!\n");
  }
  }
  }

  Close();
  }
  } catch ( _com_error e) {
  ComError(e);
  }

  return 1;
  }

  private:

  char * ReadVariableProtocol(char const * match, char * buffer, int bufferLen, long & outputLen)
  {
  char * p = NULL;
  if ( Receive((unsigned char*)buffer, bufferLen, outputLen) )
  {
  //figure out if the length bytes are leading
  if ( strncmp(buffer, match, HEADERSIZE) != 0)
  {
  //we're using the GCF, and we have length bytes prepended to the start
  p = (char *)((DEVICE_DATA*)buffer)->data;
  outputLen = outputLen - HEADERSIZE;
  }
  else
  {
  p = buffer;
  }
  printf("Received: %s\n", p);
  }
  return p;
  }

  
  bool Send(char * buf)
  {
  printf("Sending: %s\n", buf);
  HRESULT result = _channel->WritePacket((unsigned char*)buf, strlen(buf));
  return ( !FAILED(result));
  }

  bool Receive(unsigned char * buf, int len, long & actual)
  {
  switch( WaitForMultipleObjects( NUM_EVENTS, _events, FALSE, 30000 ) ) { //30 sec timeout
  case WAIT_OBJECT_0:
  try {
  HRESULT result = _channel->ReadPacket( buf, len, &actual );

  return( !FAILED( result ) );
  } catch( _com_error e ) {
  ComError( e );
  return false;
  }
  break;
  case WAIT_OBJECT_0 + 1:
  // Closed
  printf("Port closed\n" );
  return false;
  case WAIT_TIMEOUT:
  printf("Timeout waiting for inbound data\n");
  return false;
  default:
  // Shouldn't happen
  return false;
  }
  }

  void Close()
  {
  //close the channel and wait for BBDevMgr to shut it down
  _channel = NULL;

  // Wait for BbDevMgr to close the channel, otherwise it ends up crashing.
  WaitForSingleObject( _events[CLOSE_EVENT], 5000 );

  CloseHandle( _events[READ_EVENT] );
  CloseHandle( _events[CLOSE_EVENT] );
  }

  void ComError(_com_error e)
  {
  ::MessageBox(NULL, e.ErrorMessage(), "USBClient ERROR", MB_ICONERROR | MB_OK );
  }

  
  public:
  //implementation of the IChannelEvents interface
  virtual HRESULT STDMETHODCALLTYPE QueryInterface( REFIID riid, void **ppvObject )
  {
  if ( riid == IID_IChannelEvents || riid == IID_IUnknown) {
  *ppvObject = (IChannelEvents*)this;
  AddRef();
  return 0;
  }
  return E_NOINTERFACE;
  }

  virtual ULONG STDMETHODCALLTYPE AddRef()
  {
  return ++_refcount;
  }

  virtual ULONG STDMETHODCALLTYPE Release()
  {
  ULONG count = --_refcount;
  if ( count == 0 )
  {
  delete this;
  }
  return count;
  }

  virtual HRESULT STDMETHODCALLTYPE raw_CheckClientStatus( void )
  {
  return 0; //not implemented
  }

  /**
  * Called by a locked device to query for the password from the client
  * This method must write the sha_hash of the password into the provided array and return S_OK;
  * return E_FAIL to indicate an error
  */
  virtual HRESULT STDMETHODCALLTYPE raw_OnChallenge(
  /* [in] */ long attemptsRemaining,
  /* [out] */ unsigned char passwordHash[20] )
  {
  attemptsRemaining;
  char password[20];
  int passwordMax = 14;
  int exit = 0;
  int theChar = 0;
  int numChars = 0;
  static int count = 0;

  printf( "Attempt %d of 10 to enter password.\n", ++count );
  printf( "Note that the device will be wiped out after 10 failed attempts.\n\n" );
  printf( "Enter BlackBerry password: " );

  do
  {
  theChar = getch();

  //
  // user hit Enter to exit
  //
  if ( theChar == 0x0D || theChar == 0x0A )
  {
  ++exit;

  //
  // returns 0 if a function or cursor key has been hit
  // get next char to clear the scan code
  //
  } else if ( !theChar ) {
  getch();

  //
  // legit character
  // store it within the password, echo '*' to the screen
  //
  } else {
  password[numChars++] = (char)theChar;
  putch('*');
  }
  } while ( !exit && numChars < passwordMax );

  password[numChars] = 0;

  printf( "\n");

  sha_hash(password, strlen(password), passwordHash);
  return S_OK;
  }

  virtual HRESULT STDMETHODCALLTYPE raw_OnNewData( void )
  {
  SetEvent(_events[READ_EVENT]);
  return 0;
  }

  virtual HRESULT STDMETHODCALLTYPE raw_OnClose( void )
  {
  SetEvent(_events[CLOSE_EVENT]);
  return 0;
  }

  private:
  //data members
  IChannelPtr _channel;
  ULONG _refcount;
  HANDLE _events[NUM_EVENTS];

  };

  int main(int argc, char* argv[])
  {
  argc;
  argv;
  USBClient usb;
  return usb.run();
  }

  
  

• agydad

  Awesome, Thanks, I might need some later on this topic as I go along.....

  I should really say, this is the best forum...I can get all the help I want from here....

  Really appreciate guys....

  Harsimrat

  
  

• jdsouza

  By adding a reference to a COM component, you generate a stub within C#, you can't register the COM component, I don't believe, it has to be registered already. I don't think that is what you mean tho - to call the methods exposed by the component, you need to create an instance of the class that's generated for the component you referenced. You can't do anything at a finer grain than call the exposed methods.

  
  
  

• egyamado

  Once you have your C++ COM component registered, you can create instances of it and call them directly, you'll have access to all the public functions.

  
  
  

• JLB4536

  Really appreciate for your help.....

  This is my first time working something largely with COM and that to in C#. Please bear with me...

  What I did was added that .exe as a refrence. Then by #using something; ...I added to my project...How can I register the COM component and do the stuff what is done above in the code.....

  Harsimrat

  
  
• COM in C#