Skip to main content
Email Password   helpLost your password?

Introduction

This article provides a code snippet in order to programmatically send one or more files to the mail recipient, mimicking the SendTo mail recipient shell extension. I have heard many people searching for this feature, and actually I thought that, as there doesn't seem to be such source code posted on the net, I could just as well post it.

Introducing the SendTo mail shortcut

You may skip this section if you are not interested in the r.e. technique.

The SendTo mail shortcut is a shell extension. See Mike Dunn's complete idiot guide for further info.

The trick is to find out that the SendTo mail recipient shortcut is actually essentially an empty file with .MAPIMAIL as (hidden) extension name. Then, by looking up file type association in the registry (HKCR\.MAPIMAIL), it's straight forward to figure out that it is targeting a COM object with clsid = {9E56BE60-C50F-11CF-9A2C-00A0C90A90CE}. This object is sendmail.dll, a COM helper which takes advantage of either Outlook Express or Outlook to send e-mail file attachments. Next, looking up this CLSID in OLE View clearly showed that the sendmail COM component also implements the IDropTarget, IShellExtInit and IPersistFile interfaces, just like any drop handler.

Ok, basically I need to prepare a bag with dropped filenames, make sure they can be retrieved by implementing the IDataObject interface, a simple communication interface, and then mimic a standard drag and drop sequence, with two check points : DragEnter(IDataObject*) and Drop(IDataObject*).

One of the interesting points is to start implementing the IDataObject interface starting with contract, i.e. the methods it is supposed to expose. And then cowardly insert a breakpoint into any default method implementation only to get to know whether it's called or not, and in what order.

If you are interested in mimicking other SendTo shortcuts, don't hesitate to check out this registry key: HKLM\Software\Microsoft\Windows\CurrentVersion\Shell Extensions\Approved.

IDataObject implementation

The following code implements the IDataObject interface. In fact, only a few methods are required to be implemented. Those are, in order:

Because on Windows file drag-and-drop operations rely on the CF_HDROP / DROPFILES structure, we simply prepare such a structure to play with. Here is the code :

#include <windows.h>

#include <ole2.h> // IDataObject

#include <shlobj.h> // DROPFILES

#include <tchar.h> // TCHAR


class CDataObject : public IDataObject, IEnumFORMATETC
{
  // Members

protected:
  BOOL m_bReset;
  LPTSTR m_szFiles;
  int m_nLen;

    // Constructor

public:
  CDataObject(LPTSTR szFiles)
  {
    Reset();

    if (!szFiles)
    {
      m_szFiles = NULL;
      return;
    }

    // replace \n chars with \0 chars

    m_nLen = _tcslen(szFiles)+1;
    m_szFiles = new TCHAR[m_nLen];
    memcpy(m_szFiles, szFiles, m_nLen * sizeof(TCHAR));

    LPTSTR szTmp = m_szFiles;
    while ( szTmp=_tcschr(szTmp,'\n') )
      *szTmp++ = '\0';

  }

  virtual ~CDataObject()
  {
    delete [] m_szFiles;
  }

public:
  HRESULT __stdcall QueryInterface(REFIID iid, void** ppvObject)
  {
    *ppvObject = (IDataObject*) this;
    return S_OK;
  }

  ULONG __stdcall AddRef()
  {
    return 1;
  }
  ULONG __stdcall Release()
  {
    return 0;
  }



  // IDataObject implementation

  //

  HRESULT __stdcall GetData(FORMATETC* pFormatetc, STGMEDIUM* pmedium)
  {
    if (pFormatetc->cfFormat != CF_HDROP  || !pmedium)
      return S_FALSE;

    if (!m_szFiles)
      return S_FALSE; // make sure to set the files before


    pmedium->tymed = TYMED_HGLOBAL;

    // set DROPFILES structure

    HGLOBAL hglbCopy = ::GlobalAlloc(GMEM_MOVEABLE, 
                 sizeof(DROPFILES) + (m_nLen + 2) * sizeof(TCHAR)); 
    LPDROPFILES pDropFiles = (LPDROPFILES) ::GlobalLock(hglbCopy);
    pDropFiles->pFiles = sizeof(DROPFILES);
    pDropFiles->pt.x = pDropFiles->pt.y = 0;
    pDropFiles->fNC = TRUE;
    pDropFiles->fWide = FALSE; // ANSI charset

    LPTSTR lptstrCopy = (LPTSTR) pDropFiles;
    lptstrCopy += pDropFiles->pFiles;
    memcpy(lptstrCopy, m_szFiles, m_nLen * sizeof(TCHAR)); 
    lptstrCopy[m_nLen] =  '\0';    // null character 

    lptstrCopy[m_nLen+1] = '\0';    // null character 

    ::GlobalUnlock(hglbCopy); 

    pmedium->hGlobal = hglbCopy;
    pmedium->pUnkForRelease = NULL;

    return S_OK;
  }

  HRESULT __stdcall GetDataHere(FORMATETC* pFormatetc, STGMEDIUM* pmedium)
  {
    return S_OK;
  }

  HRESULT __stdcall QueryGetData(FORMATETC* pFormatetc)
  {
    return S_OK;
  }

  HRESULT __stdcall GetCanonicalFormatEtc(FORMATETC* pFormatetcIn, 
                                          FORMATETC* pFormatetcOut)
  {
    return S_OK;
  }

  HRESULT __stdcall SetData(FORMATETC* pFormatetc, 
                   STGMEDIUM* pmedium, BOOL fRelease)
  {
    return S_OK;
  }

  HRESULT __stdcall EnumFormatEtc(DWORD dwDirection, 
                        IEnumFORMATETC** ppenumFormatetc)
  {
    if (dwDirection==DATADIR_GET)
    {
      *ppenumFormatetc = this;
      return S_OK;
    }
    else
      return S_FALSE;
  }

  HRESULT __stdcall DAdvise(FORMATETC* pFormatetc, 
                            DWORD advf, 
                            IAdviseSink* pAdvSink, 
                            DWORD* pdwConnection)
  {
    return S_OK;
  }

  HRESULT __stdcall DUnadvise(DWORD dwConnection)
  {
    return S_OK;
  }

  HRESULT __stdcall EnumDAdvise(IEnumSTATDATA** ppenumAdvise)
  {
    return S_OK;
  }


  // IEnumFORMATETC implementation

  //

  HRESULT __stdcall Next( 
            /*[in]*/ ULONG celt,
            /*[out]*/ FORMATETC __RPC_FAR* rgelt,
            /*[out]*/ ULONG __RPC_FAR* pceltFetched)
  {
    if (!m_bReset) return S_FALSE;

    m_bReset = FALSE;

    FORMATETC fmt;
    fmt.cfFormat = CF_HDROP;
    fmt.dwAspect = DVASPECT_CONTENT;
    fmt.lindex = -1;
    fmt.ptd = NULL;
    fmt.tymed = TYMED_HGLOBAL;
    *rgelt = fmt; // copy struct

    if (pceltFetched) *pceltFetched = 1;

    return S_OK;
  }
        
  HRESULT __stdcall Skip(/*[in]*/ ULONG celt)
  {
    return S_FALSE;
  }
        
  HRESULT __stdcall Reset()
  {
    m_bReset = TRUE;
    return S_OK;
  }
        
  HRESULT __stdcall Clone( 
            /* [out] */ IEnumFORMATETC** ppenum)
  {
    return S_OK;
  }
};

Using it

And here is how to use it to send c:\346.jpg and c:\tmp\myfile.zip:

  ::CoInitialize(NULL);

  CDataObject cdobj("c:\\346.jpg\nC:\\tmp\\myfile.zip");
  IDataObject *pDataObject = &cdobj;


  IDropTarget *pDropTarget = NULL;

  // create an instance, and mimic drag-and-drop

  hr = ::CoCreateInstance( CLSID_SendMail, 
                         NULL, CLSCTX_ALL,
                         IID_IDropTarget, 
                         (void **)&pDropTarget);
  if (SUCCEEDED(hr))
  {
    POINTL pt = {0,0};
    DWORD dwEffect = 0;
    pDropTarget->DragEnter(pDataObject, MK_LBUTTON, pt, &dwEffect);
    pDropTarget->Drop(pDataObject, MK_LBUTTON, pt, &dwEffect);

    ::Sleep(6*1000);

    pDropTarget->Release();
  }

  ::CoUninitialize();

To compile this code, you only need WIN32.

Why SendTo is better than the mailto trick

You could tell me that shell-executing a mailto URL is just as fine, and much simpler code in practice. Yes and no. Yes, it does so, and it can't be simpler since that's only one line of code (just remember to escape ASCII chars in the body with hex replacements of the form %0D, %20, ...).

No, it does not provide support for file attachment(s), which is why the SendTo shortcut comes handy. And there is more to it. The truth is that ::ShellExecute() cannot handle parameter strings over 2048 bytes, which means your e-mail body size cannot go beyond 2048 bytes. If you try to send a large e-mail, it will result in a GPF. At this point, you could replace ::ShellExecute with a well thought ::WinExec call, using the actual mailto command line declared in the registry and target the current e-mail client (for instance, "%ProgramFiles%\Outlook Express\msimn.exe" /mailurl:%1). But then the limitation is 32 KB. As a conclusion, there is no way to send e-mails larger than 32KB using the mailto protocol. The SendTo shortcut explained in this article is definitely the way to go !

History

You must Sign In to use this message board.
 
 
Per page   
 FirstPrevNext
GeneralThe most simple solution Pin
Lord_Crow		2:57 10 Jul '09  
GeneralFabulous - but would like a small change Pin
StroudPete		4:27 14 May '09  
GeneralHelp with other send to methods Pin
WillRGV		6:20 2 Nov '07  
GeneralRe: Help with other send to methods Pin
WillRGV		7:57 2 Nov '07  
GeneralRe: Help with other send to methods Pin
jkjhcjbhj		4:25 12 Feb '08  
GeneralSendTo.exe Pin
jbergetun		2:01 5 Mar '07  
GeneralUnhandled exception in ntdll.dll Pin
Ben Kial		15:05 17 Oct '05  
GeneralNo way to specify recipient ? Pin
Weird Alexis		7:28 15 Sep '05  
GeneralRe: No way to specify recipient ? Pin
Stephane Rodriguez.		3:28 19 Sep '05  
GeneralRe: No way to specify recipient ? Pin
Weird Alexis		4:39 19 Sep '05  
GeneralRe: No way to specify recipient ? Pin
Stephane Rodriguez.		2:08 20 Sep '05  
Generaloutlook express message window is closed Pin
Anton Heidelwalder		5:01 22 Aug '05  
GeneralDoesn't work :( Pin
Andrew Ovcharov		14:00 16 Jul '05  
GeneralSame Problem Here Pin
idliiyer		11:03 3 Nov '05  
QuestionRe: Same Problem Here Pin
Ben Kial		12:17 19 Apr '07  
Generalsend mail failure --; Pin
chunghansu		22:43 13 Feb '05  
GeneralRe: send mail failure --; Pin
Stephane Rodriguez.		10:38 26 Feb '05  
GeneralC# source code Pin
Audimar		9:35 25 Jan '05  
Generalmessage body Pin
Sarfraz Anwar		22:41 15 Jun '04  
GeneralRe: message body Pin
Stephane Rodriguez.		2:06 16 Jun '04  
GeneralRe: message body Pin
Sarfraz Anwar		3:18 17 Jun '04  
GeneralRe: message body Pin
Stephane Rodriguez.		6:07 17 Jun '04  
GeneralRe: message body Pin
Andrew Foss		19:57 29 Aug '04  
GeneralRe: message body Pin
Stephane Rodriguez.		21:53 29 Aug '04  
GeneralRe: message body Pin
Andrew Foss		18:16 30 Aug '04  
Last Visit: 22:43 20 Nov '09     Last Update: 22:43 20 Nov '09 12345 Next »


Last Updated 31 Mar 2003 | Advertise | Privacy | Terms of Use | Copyright © CodeProject, 1999-2009