MFC and old functions - C / C++ / MFC Discussion Boards

Re: How to check if field value is NULL?

Imran Farooqui12-Sep-02 2:12

12-Sep-02 2:12

Consider query:

select nick from from mytable.

Suppose the value represented by nick can be NULL. So change the query as:

select isnull(nick, 'something') as nick from mytable

Here 'something' can be anything you desire. This can be a single space character also. Now when you collect value of nick from Recordset object, it'll not be null but the value supplied by you as a parmeter above. You can check it and treat as NULL

Imran Farooqui

World first Urdu Instant Messenger[^]

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Java is a tool for creating applications that torture users with its awful speed and its ugly interfaces.
Daniel Turini commenting on this article

Re: How to check if field value is NULL?

anju12-Sep-02 18:39

anju

12-Sep-02 18:39

Hi Imran Farooqui,
Thanks for Your Reply.
Please need more help to me..............
Suppose i have to select entire table then how can i make all null fields in the table to 'Something'.

in my application i am opening the recordset as follows

pRecordset->Open("mytable",
_variant_t((IDispatch*)pConnection,true),
adOpenDynamic, adLockPessimistic,adCmdTable);
and i am getting all the fields
pRecordset->MoveFirst();
while (!pRecordset->EndOfFile)
{
strTemp.Format("Field1:%s",(LPSTR)(_bstr_t)pRecordset->Fields->GetItem("Field1")->Value);
AfxMessageBox(strTemp);
pRecordset->MoveNext();
}
Rose | [Rose]

anju

Re: How to check if field value is NULL?

Imran Farooqui12-Sep-02 19:06

Imran Farooqui

12-Sep-02 19:06

In your code, you'r opening a complete table using RecordSet object. I do not prefer this technique because you have no control over the selected records. Instead i prefer to explicitly open the table using SQL queries.

m_pRecordSet = m_pConnection->Execute("select * from mytable", &vRecsAffected, adOptionUnspecified);

Only if you are accessing the table in this way, you can use, isnull option.

Imran Farooqui

World first Urdu Instant Messenger[^]

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Java is a tool for creating applications that torture users with its awful speed and its ugly interfaces.
Daniel Turini commenting on this article

Re: How to check if field value is NULL?

Rama Krishna Vavilala12-Sep-02 2:09

Rama Krishna Vavilala

12-Sep-02 2:09

You need to do something like this.

_variant_t vt = pRecordset->Fields->GetItem("Test")->Value;

if (vt.vt == VT_NULL)
{
  AfxMessageBox("Field is NULL");
}
else
{
strTemp.Format("Test Column:%s",(LPSTR)(_bstr_t)vt); 
AfxMessageBox(strTemp);
}

C# is fundamentally broken. - Christian Graus

Re: How to check if field value is NULL?

[James Pullicino]12-Sep-02 2:36

[James Pullicino]

12-Sep-02 2:36

This line:

<br />
(LPSTR)(_bstr_t)pRecordset->Fields->GetItem("Test")->Value); <br />

is very dangerous because of the following reasons:

If Fields fails, an exception will be thrown.
If GetItem fails, an exception will be thrown.
If Value cannot be converted to a _bstr_t, an exception will be thrown.

Segment your code a little better. Add exception handling, or use the raw_ methods of your smart pointers. Here is an example on how to improve your code (this is from memory):

<br />
IFieldPtr field;<br />
try<br />
{<br />
  field = pRecordset->Fields->GetItem("Test");<br />
} <br />
catch(com_error e) <br />
{ <br />
  field = NULL;<br />
}<br />
<br />
if(field != NULL)<br />
{<br />
  _variant_t vtVal;<br />
  try<br />
  {<br />
    vtVal = field->Value;<br />
  } catch (_com_error e) {vtVal.vt = VT_ERROR; }<br />
  <br />
  _bstr_t bstrVal;<br />
  if(vtVal.vt != VT_ERROR)<br />
  {<br />
     try{ bstrVal = (_bstr_t)vtVal; }<br />
     catch(com_error e) {bstrVal = L"";}<br />
  }<br />
  <br />
  AfxMessageBox((LPCTSTR)bstrVal);<br />
}<br />
<br />

--James

Drinking In The Sun
Forgot Password?

Re: How to check if field value is NULL?

anju12-Sep-02 18:44

anju

12-Sep-02 18:44

Hi Rama Krishna,
ThankQ this technique is work to me well
Rose | [Rose]

anju

Re: How to check if field value is NULL?

anju12-Sep-02 18:51

anju

12-Sep-02 18:51

Hi James Pullicino,
Thanks a lot..
I never thing about what u pointed.
now my code is changed as per your instructions.
once again thank to you
Rose | [Rose]

anju

MFC and old functions

Tolias12-Sep-02 1:38

Tolias

12-Sep-02 1:38

I need to ask a question that's been bothering me for some time now. I created an SDI application from the Visual C++ wizard. Everything was fine then. When I added a function (that someone else) created in old C, all of a sudden the menu and status bar dissapeared and I haven't seen them since then. I get no errors after building the project but I can't make the bars appear, neither through menu->view nor with right clicking. Could it be that some old function (like atoi) has a side-effect on the program? All functions in the old C file are global to the project.

Re: MFC and old functions

Tomasz Sowinski12-Sep-02 1:42

Tomasz Sowinski

12-Sep-02 1:42

Sounds strange. 'Old functions like atoi' shouldn't have any side-effects. What is the purpose of function you've added?

Tomasz Sowinski -- http://www.shooltz.com

To some its a six-pack, to me it's a support group

Re: MFC and old functions

Anonymous12-Sep-02 1:52

Anonymous

12-Sep-02 1:52

It reads two files containing neurules definitions and variable definitions, asks the user to insert values to variables and then uses the neurules to make an inference. It also evaluates the rules if needed. My part was to convert all the 'printf' calls to something visual.

Re: MFC and old functions

Tomasz Sowinski12-Sep-02 1:54

Tomasz Sowinski

12-Sep-02 1:54

At what point exactly are you calling this function? Are you using dialogs for entering variables' values?

Tomasz Sowinski -- http://www.shooltz.com

To some its a six-pack, to me it's a support group

Re: MFC and old functions

Tolias12-Sep-02 1:59

Tolias

12-Sep-02 1:59

Well, this function was originally writen in C with a console user interface. I erased all printf and scanf calls and used dialogs to prompt messages and get input. The function is called inside ON_OPTIONS_INFERENCE.

Re: MFC and old functions

Tomasz Sowinski12-Sep-02 2:03

Tomasz Sowinski

12-Sep-02 2:03

It shouldn't have side-effects you've described. I guess you'll have to look for the cause of problems by commenting out parts of the code or inserting temporary return statements.

Tomasz Sowinski -- http://www.shooltz.com

To some its a six-pack, to me it's a support group

Re: MFC and old functions

Michael P Butler12-Sep-02 1:44

Michael P Butler

12-Sep-02 1:44

Put a breakpoint in the CMainFrame::OnCreate function. This is where the toolbar and status bar should be created. It should give you more of a clue to why they have gone.

Michael

Programming is great. First they pay you to introduce bugs into software. Then they pay you to remove them again.

Compiler directives

Ruca12-Sep-02 1:20

Ruca

12-Sep-02 1:20

Hi,
I have 2 projects ( project A and B)which use most of the same functions, but there are others which are unique to project A and others to B.
I would like to be able to use a #define to compile Project A with its own functions and then by changing the #define compile project B with its functions. In other words, I would like to avoid defining 2 different projects.
Is this possible?
And how does one do it, both in the header and source code files?

Thanking you in anticipation.

Rui

Re: Compiler directives

Tomasz Sowinski12-Sep-02 1:29

Tomasz Sowinski

12-Sep-02 1:29

You can use #ifdef and friends for conditional compilation. Your other option is to create a library containing common code.

Tomasz Sowinski -- http://www.shooltz.com

To some its a six-pack, to me it's a support group

Ouput data

Kash12-Sep-02 1:15

Kash

12-Sep-02 1:15

I am running numerical code and want to print the results in a scrollable edit box and I want to save this data in an array?

Any ideas?

Kash

Re: Ouput data

Christian Graus12-Sep-02 2:10

Christian Graus

12-Sep-02 2:10

iostreams - check out my articles here on CP.

Christian

Hey, at least Logo had, at it's inception, a mechanical turtle. VB has always lacked even that... - Shog9 04-09-2002

During last 10 years, with invention of VB and similar programming environments, every ill-educated moron became able to develop software. - Alex E. - 12-Sept-2002

Re: Ouput data

Jawache12-Sep-02 3:28

Jawache

12-Sep-02 3:28

Too Vague Kash.

Ask something more specific or give more details.

Asim Hussain
e: asim@jawache.net
w: www.jawache.net

Splitter Window with 2 views with MFC

Chun Te, Ewe12-Sep-02 0:58

Chun Te, Ewe

12-Sep-02 0:58

Dear All,

I would like to have 2 different views for a document. Each view to be display one at a time or together using a splitter window at any point of time.

How best should I approach this? I'm open to any new ideas.

I've just started programming and I think my question will be trivial to most of you out there. Thanks very much for taking the time to help me out

Regards,
Chun Te

Re: Splitter Window with 2 views with MFC

Jawache12-Sep-02 1:14

Jawache

12-Sep-02 1:14

If when you say different views you mean, different view classes, then you should use a Splitter Window and create static views, look at MSDN.

Its difficult to create a Static Splitter window which can turn into a single window since the Splitter Asserts if there is only once view. have a look in the Splitter Section of codeproject.. there might be some ideas you can use.

Asim Hussain
e: asim@jawache.net
w: www.jawache.net

Re: Splitter Window with 2 views with MFC

JohnnyG12-Sep-02 2:37

JohnnyG

12-Sep-02 2:37

I've used this class, ST_SplitterWnd,to do just what you want. I have two views which are the same because the view has a tab control. The dual views allows the user to see two different tabs of data at once, if desired.

It is here on Code Project in the Articles section. BTW, the class has a nice function called ToggleSide() which allows hiding one of the views. Thus, you can add both views and hide one and the user only sees one. But, when the user wants a second view, you just call ToggleSide() again.

Dll in release mode....

Neha12-Sep-02 0:39

Neha

12-Sep-02 0:39

Hi,
I have written a MFC Extended dll.It works fine in Debug mode.In Release mode if i use /MDd it works.But if i use /MD it crashes. Could any one pl tell me why is it happening so?

Thanks
Neha

Re: Dll in release mode....

Tomasz Sowinski12-Sep-02 0:45

Tomasz Sowinski

12-Sep-02 0:45

You have probably screwed something with project settings. What exactly crashes?

Tomasz Sowinski -- http://www.shooltz.com

To some its a six-pack, to me it's a support group

Re: Dll in release mode....

Neha12-Sep-02 0:53

Neha

12-Sep-02 0:53

A third party dll(IMGSCAN.OCX)loads my dll(It is a TWAIN Datasource).If i use /MD configuration it says access violation in imgscan.ocx .

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.