C / C++ / MFC

Re: Not able to connect to the database [modified]

13-May-09 19:45

vital_parsley2000 wrote:
where do i insert this code ?

In your source files, dear!

It is a function, you can either put it in your .cpp file or .h file in global scope or add as a member function in your class.

Am I missing something ?

Madhu Nair13-May-09 20:03

Re: Not able to connect to the database

13-May-09 20:03

Another Tip:

Put the variable hr in the debug watch window, append ", hr" (without the quotes) to it to have Visual C++ translate it for you!

Or you can use pseudo variable $err as $err,hr in Watch window.The $err pseudo variable provides the value, and the hr format specifier tells the watch window to format it as an error code.

http://i.msdn.microsoft.com/dd252945.fig05_L(en-us).gif[^]

modified on Thursday, May 14, 2009 2:21 AM

David Crow13-May-09 3:17

David Crow

13-May-09 3:17

vital_parsley2000 wrote:
In the above code the if(SUCCEEDED(hr)) block is not executed.

Which one?

vital_parsley2000 wrote:
What could be the reason ?

CreateInstance() or Open() failed and control did not return to the subsequent if() statement.

"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown

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Load data from database to BCG grid

MrKBA12-May-09 21:56

12-May-09 21:56

Hi,
I'm developing an application and i would display data from database(access, sqlserver, oracle) in a bcg grid.
So can someone help me by a simple example of code or how can i do for this.

Thank you very much. Smile | :)

Madhu Nair12-May-09 22:14

12-May-09 22:14

khaliloenit wrote:
So can someone help me by a simple example of code

Using MS DataGrid control with ADO[^]

Also look at the DataGrid Control[^] MSDN

MrKBA12-May-09 22:27

12-May-09 22:27

is this solution will work with SqlServer and Oracle database ?

Rajesh R Subramanian12-May-09 22:32

Rajesh R Subramanian

12-May-09 22:32

khaliloenit wrote:
is this solution will work with SqlServer and Oracle database ?

Had you bothered to go through the links given to you, then you would have noticed the answer to your same exact question in the CP article:

"The sample has been tested with both MS Access and SQL Server, in theory you should be able to use it against all data sources that support OLE-DB."

It is a crappy thing, but it's life -^ Carlo Pallini

MrKBA12-May-09 22:37

12-May-09 22:37

Sorry, but there is a solution with BCG Grid?

MrKBA13-May-09 22:47

13-May-09 22:47

Please i try to use MS DataGrid in the Using MS DataGrid control with ADO[^] but i work with VS2003 and i don't find where i can add the Microsoft datagrid control with ADO !!!!?
So can you help me

Append BStr

Mogaambo12-May-09 21:23

12-May-09 21:23

Below is the code to append Bstr, but in debug mode it gives error
' ::SysFreeString(dest); ' and in release mode if i dont write ' ::SysFreeString(dest); ' it corrupts heap. What optimization i do.

BSTR StringAppend(const BSTR dest,const BSTR src)
{
long destLen=::SysStringByteLen(dest);
long srcLen=::SysStringByteLen(src);

BSTR st3 = ::SysAllocStringByteLen(NULL,destLen+srcLen);
try
{
if(st3==NULL)
{
throw "Insufficient Memory";
}
else
{
wcscpy(st3, dest);
wcscat(st3, src);
::SysFreeString(dest);// here it gives error in debug mode
}
}
catch(char * error)
{
throw error;
}

return st3;
}

“You will never be a leader unless you first learn to follow and be led.”
–Tiorio

"Coming together is a beginning, staying together is progress, and working together is success." Henry Ford

Madhu Nair12-May-09 21:27

12-May-09 21:27

A const BSTR dest ?
Why const ?

CPallini12-May-09 21:31

12-May-09 21:31

Why are you freeing dest?

Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Mogaambo12-May-09 22:26

12-May-09 22:26

CPallini wrote:
Why are you freeing dest?

Because if i do not free, it gives error that heap is violated in release mode and when i traced down it goes in the NULL condition.

“You will never be a leader unless you first learn to follow and be led.”
–Tiorio

"Coming together is a beginning, staying together is progress, and working together is success." Henry Ford

CPallini12-May-09 22:33

12-May-09 22:33

Please show us the calling code.
Smile | :)

Mogaambo12-May-09 22:36

12-May-09 22:36

Here is my calling code. value variable is of type BSTR

BSTR GetNewRow()
{
value=GetLoggedInUser();

BSTR strComma=::SysAllocString(L",");
BSTR strNewLine=::SysAllocString(L"\n");

value=StringAppend(value,strComma);

value=StringAppend(value,strCategory);
value=StringAppend(value,strComma);
value=StringAppend(value,strItemName);
value=StringAppend(value,strComma);
value=StringAppend(value,strInstallDate);
value=StringAppend(value,strComma);
value=StringAppend(value,strVersion);
value=StringAppend(value,strComma);
value=StringAppend(value,strValue1);
value=StringAppend(value,strComma);
value=StringAppend(value,strValue2);
value=StringAppend(value,strComma);
value=StringAppend(value,strValue3);
value=StringAppend(value,strNewLine);

::SysFreeString(strComma);
::SysFreeString(strNewLine);

return value;
}

“You will never be a leader unless you first learn to follow and be led.”
–Tiorio

"Coming together is a beginning, staying together is progress, and working together is success." Henry Ford

CPallini12-May-09 23:14

12-May-09 23:14

It looks like the problem is in your bad mixing of char and wchar calls:
with the following line

BSTR st3 = ::SysAllocStringByteLen(NULL,destLen+srcLen);

you're allocating (destLen + srcLen + 1) bytes.

while in the following calls

wcscpy(st3, dest);
wcscat(st3, src);

you need, (destLen + srcLen + 2) bytes.

Smile | :)

Mogaambo12-May-09 23:54

12-May-09 23:54

Thanks working great now .

i don't know the +2 funda , actually i am c# developer but my firm wants me to develop project in c++.

::SysFreeString(dest);

can i free this in StringAppend function itself or after my function returns.

“You will never be a leader unless you first learn to follow and be led.”
–Tiorio

"Coming together is a beginning, staying together is progress, and working together is success." Henry Ford

CPallini13-May-09 0:06

13-May-09 0:06

Technically you can do it inside. However you probably should revise your design, for instance using a prototype like the following for your function:

HRESULT StringAppend( BSTR * pdst, const BSTR src);

or, better, using, as suggested, the handy _bstr_t wrapper.
Smile | :)

Mogaambo13-May-09 0:19

Re: Append BStr [modified]

13-May-09 0:19

1. BSTR * pdst

why pointer here.

BSTR is itself a pointer.

2. What code you have write for StringAppend function ?

I want to take some idea from you.It would be very helpful for me.It's a humble request from a programmer to a professional.

“You will never be a leader unless you first learn to follow and be led.”
–Tiorio

"Coming together is a beginning, staying together is progress, and working together is success." Henry Ford

CPallini13-May-09 0:39

13-May-09 0:39

Mogaambo wrote:
1. BSTR * pdst

why pointer here.

BSTR is itself a pointer.

Because the function will internally change the value of the original pointer, i.e. pdst is a INOUT parameter (this way you state clearly that the function may alter the original dst string).

Mogaambo wrote:

2. What code you have write for StringAppend function ?

Something like

HRESULT StringAppend(BSTR * pdest, const BSTR src)
{
 if (pdest == NULL) return E_FAIL;
 long destLen=::SysStringLen(*pdest);
 long srcLen=::SysStringLen(src);

 BSTR tmp = ::SysAllocStringLen(NULL,destLen+srcLen);
 if( tmp == NULL) return E_FAIL;
 wcscpy(tmp, *pdest);
 wcscat(tmp, src);
 ::SysFreeString(*pdest);
 
 pdest = &tmp;
 *pdest = tmp;
 return S_OK;
}

Beware: I didn't check this code (moreover I've used just the very basic E_FAIL failure
return value, a good function should be more informative on failure.

modified on Wednesday, May 13, 2009 8:02 AM

Mogaambo13-May-09 0:53

13-May-09 0:53

BSTR tmp = ::SysAllocStringLen(NULL,destLen+srcLen);
dude you haven't added +2 bytes, it is crashing as that of mine, but when i added +2 it is running fine, so whenever i want allocate BSTR do i have 2 add + bytes.

BSTR tmp = ::SysAllocStringLen(NULL,destLen+srcLen+2);

“You will never be a leader unless you first learn to follow and be led.”
–Tiorio

"Coming together is a beginning, staying together is progress, and working together is success." Henry Ford

CPallini13-May-09 1:33

13-May-09 1:33

Mogaambo wrote:
dude you haven't added +2 bytes

I know, I don't need to (I'm using SysAllocStringLen, not SysAllocStringByteLen).

Mogaambo wrote:
it is crashing as that of mine, but when i added +2 it is running fine

This is very strange.

Mogaambo wrote:
so whenever i want allocate BSTR do i have 2 add + bytes

Nope. Even if your point about the crash is true (and is true, I know) this is a wrong conclusion.
Smile | :)

CPallini13-May-09 2:08

13-May-09 2:08

I made a silly error in my code, now fixed (please see again the posted snippet).
It should be OK now, the following test runs fine:

BSTR dest = SysAllocString(L"Hi ");
BSTR s1,s2,s3,s4;
s1 = SysAllocString(L"People, ");
s2 = SysAllocString(L"How do ");
s3 = SysAllocString(L"you ");
s4 = SysAllocString(L"do?");
HRESULT hr;
hr = StringAppend(&dest, s1);
hr = StringAppend(&dest, s2);
hr = StringAppend(&dest, s3);
hr = StringAppend(&dest, s4);

MessageBoxW(dest, L"Info");

SysFreeString(s1);
SysFreeString(s2);
SysFreeString(s3);
SysFreeString(s4);
SysFreeString(dest);

Mogaambo13-May-09 2:37

13-May-09 2:37

If you run your code in debug mode , it crashes at line where you freeing the variable, but runs in release mode.

“You will never be a leader unless you first learn to follow and be led.”
–Tiorio

"Coming together is a beginning, staying together is progress, and working together is success." Henry Ford

CPallini13-May-09 2:43