Re: convert CString to a _bstr_t - how to? - C / C++ / MFC Discussion Boards

convert CString to a _bstr_t - how to?

ns19-Sep-02 1:00

19-Sep-02 1:00

How do I convert a CString to a _bstr_t?

Thanks,
ns

Re: convert CString to a _bstr_t - how to?

dabs19-Sep-02 1:25

dabs

19-Sep-02 1:25

_bstr_t bstrText = L"text";
//You can let CString do the conversion from wchar to char:
CString strText = (LPCWSTR)bstrText;
//or let _bstr_t do it:
CString strText2 = (LPCSTR)bstrText;

Wenn ist das Nunstück git und Slotermeyer? Ja! Beierhund das oder die Flipperwaldt gersput!

Re: convert CString to a _bstr_t - how to?

ns19-Sep-02 1:31

19-Sep-02 1:31

The other way round:

I have CString a ="abc";

I want to make this a _bstr_t, so that I have:

_bstr_t ab = SOmethingDoneTo (a)

Thanks,
ns

Re: convert CString to a _bstr_t - how to?

ns19-Sep-02 1:32

19-Sep-02 1:32

Incidentally, whats the L mean here from your snippet?

L"text";

Thanks,
ns

Re: convert CString to a _bstr_t - how to?

dabs19-Sep-02 1:39

dabs

19-Sep-02 1:39

To answer both of your questions:

ns wrote:
Incidentally, whats the L mean here from your snippet?

It means that the hardcoded text shall be interpreted as a string of wchar - not char. In other words:

char* pszText = "this is a text"; //This works
wchar_t* pszwText = L"so is this"; //This works also

char* pszText2 = L"doesn't work"; 
//This generates a compiler error - can't convert from wchar to char

wchar* pszwText2 = "doesn't work either"
//this also generates compiler error.

To answer your other question - to convert from CString to _bstr_t you can use:

CString strText = _T("This is a text");
_bstr_t bstrText = (LPCTSTR)strText;
//Now _bstr_t will construct itself from a LPCTSTR - ususally a const char*

Wenn ist das Nunstück git und Slotermeyer? Ja! Beierhund das oder die Flipperwaldt gersput!

Re: convert CString to a _bstr_t - how to?

Trollslayer19-Sep-02 1:42

Trollslayer

19-Sep-02 1:42

Here is a code fragment:

void CShelf2Dlg::OutStr(CString Str, int Port)
{
VARIANT va;

va.vt = VT_BSTR; // The variant is storing a string
va.bstrVal = Str.AllocSysString(); // Convert the CString to the VARIANT
Comport[Port]->SetOutput(va); // and output it

}

Elaine (fluffy tigress emoticon)

Would you like to meet my teddy bear ?

Re: convert CString to a _bstr_t - how to?

ns19-Sep-02 1:53

19-Sep-02 1:53

Well, I did

_bstr_t b_dataBaseName = SysAllocString (dataBaseName);

where dataBaseName is a char* and get the error:

error C2664: 'SysAllocString' : cannot convert parameter 1 from 'char *' to 'const unsigned short *'

Thanks,
ns

Re: convert CString to a _bstr_t - how to?

dabs19-Sep-02 1:58

dabs

19-Sep-02 1:58

This will work but your program will leak memory. ::SysAllocString allocates a BSTR and you are assigning it to a _bstr_t. _bstr_t does not take ownership of the BSTR however so you would have to release it using ::SysFreeString( ).

Yet another way would be to use the USES_CONVERSION macros defined in atlconv.h - your code would then look like:

USES_CONVERSION;

_bstr_t b_databaseName = T2W( dataBaseName );

Hope this helps,
- d a b s -

Wenn ist das Nunstück git und Slotermeyer? Ja! Beierhund das oder die Flipperwaldt gersput!

Re: convert CString to a _bstr_t - how to?

ns19-Sep-02 2:13

19-Sep-02 2:13

I tried both your ideas, (freeing the bstr also), but I got from the atlconv idea:

error C2664: 'MakeDB' : cannot convert parameter 1 from 'class _bstr_t' to 'unsigned short ** '

I must be doing something incredibly dumb....

	  char* dataBaseName = new char[dataBaseName0.GetLength() +1];

	  strcpy(dataBaseName, dataBaseName0);
	
//	  BSTR b_dataBaseName = SysAllocString (dataBaseName);

	  USES_CONVERSION;
	  
	  _bstr_t b_dataBaseName = T2W( dataBaseName );
	   char* strFile = new char[strFile0.GetLength() +1];

	  strcpy(strFile, strFile0);

//	  _bstr_t b_strFile = SysAllocString (strFile);

	  _bstr_t b_strFile = T2W(strFile);

      _Class1Ptr ptr;
 
       ptr.CreateInstance(__uuidof(Class1));

        ptr->MakeDB( b_strFile, b_dataBaseName);

//	      ptr->MakeDB( LPCTSTR(strFile), LPCTSTR(dataBaseName));

//		SysFreeString (b_dataBaseName);

//		SysFreeString (b_strFile);

                delete[] etc

Thanks for all the help so far....

Thanks,
ns

Re: convert CString to a _bstr_t - how to?

dabs19-Sep-02 2:17

dabs

19-Sep-02 2:17

This is probably the easiest way to do it:

USES_CONVERSION;

LPCWSTR pszwDatabaseName = T2W( (LPCTSTR)dataBaseName0 );
LPCWSTR pszwFileName = T2W( (LPCTSTR)strFile0 );

_Class1Ptr ptr;        
ptr.CreateInstance(__uuidof(Class1));
ptr->MakeDB( pszwFileName, pszwDatabaseName );

Wenn ist das Nunstück git und Slotermeyer? Ja! Beierhund das oder die Flipperwaldt gersput!

aaargh!!

ns19-Sep-02 2:32

19-Sep-02 2:32

Did your latest idea:

error C2664: 'MakeDB' : cannot convert parameter 1 from 'const unsigned short *' to 'unsigned short **

for my VB function:

Public Function MakeDB(txtPMAFilename As String, dataBaseName As String)

why does it think vb String is 'unsigned short **'?

I've tried so many different ideas from all the supportive replies, but seem to be stumped!

Thanks,
ns

I think I might have got it....

ns19-Sep-02 3:04

19-Sep-02 3:04

I had to change the vb parameters to byval....now it compiles. May or may not run but at least it compiled! Sorry for all the bother and thanks for all the help!!!

ns

Thanks,
ns

Re: convert CString to a _bstr_t - how to?

ns19-Sep-02 7:32

19-Sep-02 7:32

SInce the resolution was to code the VB function parameter as ByVal, does this mean that _bstr_t variables can only be passed in by value? What if we wanted to change a _bstr_t variable in the VB dll so that the changes would be reflected in the VC side?
Puzzled,
Thanks,
ns

Thanks,
ns

handle

Anonymous19-Sep-02 0:33

Anonymous

19-Sep-02 0:33

How to get the handle of a previous appln window

Re: handle

super19-Sep-02 1:08

super

19-Sep-02 1:08

Can u be more precise.. Confused | :confused:

I didnt get u......

cheers,
Super
------------------------------------------
Too much of good is bad,mix some evil in it

Re: handle

dabs19-Sep-02 1:33

dabs

19-Sep-02 1:33

If you are trying to create a singleton application then this is not the best way to do it. There are articles here about this - the best one is probably by Joseph Newcomer - can't remember the URL.

If however you want to find out the handle to a previous instance of your app window you can always use ::FindWindow( ). You must know the WNDCLASS of your main window to do this and to complicate matters even more you will probably have to think about the case when there are more than one previous windows around.

Example: to find a running instance of Excel you can use:

HWND hWndExcel = ::FindWindow( _T("XLMAIN"), NULL );

Then if you want to find a window with a special window caption - say you know the Excel instance you want to find has the file "secrets.xls" open you could use this:

HWND hWndExcel = ::FindWindow( _T("XLMAIN"), _T("Microsoft Excel - secrets.xls") );

Hope this helps somewhat,

- d a b s -

Wenn ist das Nunstück git und Slotermeyer? Ja! Beierhund das oder die Flipperwaldt gersput!

copy to clipboard

Safder18-Sep-02 23:30

Safder

18-Sep-02 23:30

I have a large client area, and scroll bars are needed to view it all. Using the normal code puts only the visible area in the clipboars. I need to dump the visible as well as the non-visible part of the client area on to the clipboard. Please help!!!

Platform question

Anonymous18-Sep-02 23:24

Anonymous

18-Sep-02 23:24

I made an app that can run on Win9x/Win2k.

I want that on Win2k my dialog become transparent, so I used the fonction SetLayeredWindowAttributes(...). It won't compile, I've added /D "_WIN32_WINNT=0x0500" to the compiler additional Options, now it compils but don't work on Win9x...

Is it a way to make my app work on all Windows ?

Re: Platform question

Lakitu18-Sep-02 23:36

Lakitu

18-Sep-02 23:36

Unfortunately not... Transpareny was introduced in W2K (WinNT 5.0)

Re: Platform question

Anonymous18-Sep-02 23:49

Anonymous

18-Sep-02 23:49

Yes I know, but I thought that the app can run on Win9x and the fonction simply ignored....

And I know I can load SetLayeredWindowAttributes directly from "User32.dll" with LoadLibrary blabla, but I was asking if there is a solution to simply use SetLayeredWindowAttributes (I don't need to load it from User32.dll because I have the last Platform SDK) and make my app run on all Windows (and the fonction does nothing on Win9x).

Ouch sorry for my english I hope someone will understand what I want to say ;o)

Anyway, Lakitu thanks for your answer.

Re: Platform question

Stephane Rodriguez.18-Sep-02 23:59

Stephane Rodriguez.

18-Sep-02 23:59

OSVERSIONINFO os;
::GetVersionEx(&os);

if ( os.dwMajorVersion>=5 )
   SetLayeredWindowAttributes(...).

MS quote (http://www.microsoft.com/ddk) : As of September 30, 2002, the Microsoft® Windows® 2000 DDK, the Microsoft Windows 98 DDK, and the Microsoft Windows NT® 4.0 DDK will no longer be available for purchase or download on this site.

Re: Platform question

Anonymous19-Sep-02 0:04

Anonymous

19-Sep-02 0:04

Yes I know this code, but it doesn't solve my problem !
To compile it I have to set /D "_WIN32_WINNT=0x0500" but when I set that it doesn't work on Win9x :-/

Re: Platform question

Stephane Rodriguez.19-Sep-02 0:22

Stephane Rodriguez.

19-Sep-02 0:22

Put this code in a separate DLL. And make two versions of this DLL, one without _WIN32_WINNT=0x0500. From your main app, you then just need to load the appropriate DLL depending on the os version.
This DLL remains small, which is may be a better approach than having two whole apps compiled for each target os.

Re: Platform question

Steve S19-Sep-02 6:31

Steve S

19-Sep-02 6:31

The alternative is to write a wrapper function for the one you're trying to use, which detects the OS version and if it's Win2000/XP or later, gets the address of the function from USER32 and calls it, otherwise does nothing.

Your problem is two things;

You don't have the function declaration unless you have _WIN32_WINNT set to 0x0500, and with that in place, you have a reference to the function in your EXE.

When the EXE runs on an earlier (NT,9x) system, the function cannot be located by the import lib code you pulled in when you built.

You can either do what Stephane suggests, what I suggest, or not use the function Smile | :)

Steve S
[This signature space available for rent]

Re: Platform question

Atlantys19-Sep-02 10:31

Atlantys

19-Sep-02 10:31

give this a try: http://www.codeproject.com/dialog/clayeredwindowhelperst.asp[^]

He basically does everything that you're having problems with.

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