Getting the Combo Box selected item using Win32 API.

Suresh H

Hello All, I am adding values 0,1,2 to a combo box in Initdialog switch(Message) { case WM_INITDIALOG: { HWND hwndCombo = GetDlgItem(hwnd, IDC_CB); SendMessage(hwndCombo , CB_ADDSTRING,0, (LPARAM) "0"); SendMessage(hwndCombo , CB_ADDSTRING,0, (LPARAM) "1"); SendMessage(hwndCombo , CB_ADDSTRING,0, (LPARAM) "2"); } in other function I want to use the value of the combo box, (user selected item) for that I am using below code int F; HWND HCBF = GetDlgItem(hwnd, IDC_CB); SendMessage(HCBF , CB_GETITEMDATA,(WPARAM)F, 0); This code has no error but I am getting some junk value and i am not geting the values 0,1,2 Can u please tell me what is the error in the above code ??? Thanking you, Suresh HC.

prasad_som

Suresh H wrote:

int F; HWND HCBF = GetDlgItem(hwnd, IDC_CB); SendMessage(HCBF , CB_GETITEMDATA,(WPARAM)F, 0);

Here , you have not initialized F. Passing junk values as index. Pass index you want there. CB_GETITEMDATA is not right message to send in this case, too. You need to use CB_GETLBTEXT.

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Suresh H

Hi Prasad, Thanks for the response. Actually I want to extract the value of the Combo Box (user selected value) In combo box we have values from 0,1,2,3 ---- so on when user selects some value fro list any number , I want to extract that number and I want to use that number in the program. Can u please tell me what I have to do ??

Hamid Taebi

You must use of CB_GETCURSEL for get index to currently selected item instead use of 0

WhiteSky

prasad_som

This code should suffice,

int nIndx =::SendMessage(hCombo,CB_GETCURSEL,0,0);
TCHAR buff[100];
::SendMessage(h,CB_GETLBTEXT,(WPARAM)nIndx,(LPARAM)buff);
//buff will contain text returned

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Hamid Taebi

And he needs to a convert atoi ;)

WhiteSky

prasad_som

WhiteSky wrote:

And he needs to a convert atoi

Why ?

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Suresh H

Thanks Prasad Code is working. Thanks for taking some time for me and helping me. In yr code 1st line was enough for me int nIndx =::SendMessage(hCombo,CB_GETCURSEL,0,0); since in the combo box I have values from 0,1,2,3,4,5 and so on … so as I get the Index number value will be the same as the CB content. I did not know about the CB index. Thank you very much.:)

Hamid Taebi

If he wants to use of numeric values

WhiteSky

Suresh H

Thanks WhiteSky for the Response, yr info is also very use full for me. I will keep a note of that.

prasad_som

Ok, you was refering to extracting numbers.

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prasad_som

Suresh H wrote:

since in the combo box I have values from 0,1,2,3,4,5 and so on … so as I get the Index number value will be the same as the CB content.

Seems very strange logic. But, use CB_GETLBTEXT message, as it will not be the case always.

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Hamid Taebi

And also one other thing if he wants to use CB_GETCURSEL(return values) for works on his programs(not for combobox)its not good idea because it returns -1,0,1,...but if he has values like 100,200,300 on his combobox... return values of CB_GETCURSEL not helpfuls ;)

WhiteSky

Suresh H

Yes Prasad I will make use of it.

Hamid Taebi

Thank you ;)

WhiteSky

prasad_som

WhiteSky wrote:

CB_GETCURSEL(return values) for works on his programs(not for combobox)

:confused:

WhiteSky wrote:

its not good idea because it returns -1,0,1,...but if he has values like 100,200,300 on his combobox... return values of CB_GETCURSEL not helpfuls

I'm really not getting , what you are trying to say?

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Hamid Taebi

I said its better he uses of value on combobox ;)

WhiteSky

prasad_som

Haven't you seen this[^]?

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jhwurmbach

For CB_GETLBTEXT, MSDn says: lParam Pointer to the buffer that receives the string. The buffer must have sufficient space for the string and a terminating null character. With your 100 TCHARS you might or might not be ok. MSDN gives the solution in the next sentence: You can send a CB_GETLBTEXTLEN message prior to the CB_GETLBTEXT message to retrieve the length, in TCHARs, of the string. So, the code-snippet would better be:

int nIndx =::SendMessage(hCombo,CB_GETCURSEL,0,0);
const LRESULT nSize = ::SendMessage(hCombo, CB_GETLBTEXTLEN, (WPARAM)nIndx, 0);
TCHAR buff[nSize+1];
::SendMessage(h,CB_GETLBTEXT,(WPARAM)nIndx,(LPARAM)buff);
//buff will contain text returned

"We trained hard, but it seemed that every time we were beginning to form up into teams we would be reorganised. I was to learn later in life that we tend to meet any new situation by reorganising: and a wonderful method it can be for creating the illusion of progress, while producing confusion, inefficiency and demoralisation." -- Caius Petronius, Roman Consul, 66 A.D.

prasad_som

jhwurmbach wrote:

lParam Pointer to the buffer that receives the string. The buffer must have sufficient space for the string and a terminating null character. With your 100 TCHARS you might or might not be ok.

True, It is just a quick fix.

jhwurmbach wrote:

TCHAR buff[nSize+1];::SendMessage(h,CB_GETLBTEXT,(WPARAM)nIndx,(LPARAM)buff);//buff will contain text returned

Again, small correction here, need to allocate memory on heap.

 TCHAR \*buff = new TCHAR\[nIndx+1\];
::SendMessage(hCombo,CB\_GETLBTEXT,(WPARAM)0,(LPARAM)buff);
//use delete \[\] buff; after use

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