Messagebox detect YesNoCancel button

Question

I am using a VCL Forms application in C++ Builder. can I please have some help in some code to display a messagebox with YesNoCancel buttons and then detect if the yes, the no or the cancel button is pressed.

Here is my code:

if(MessageBox(NULL, "Test message", "test title",  MB_YESNOCANCEL) == IDYES)
{

}

I have included the following:

#include <windows.h>

I am getting the following errors:

E2034 Cannot convert 'char const[13]' to 'const wchar_t *'

E2342 Type mismatch in parameter 'lpText' (wanted 'const wchar_t *', got 'const char *')

Update

Here is my code:

const int result = MessageBox(NULL, L"You have " + integerNumberOfImportantAppointments + " important appointments. Do you wish to view them?", L"test title",  MB_YESNOCANCEL);

The value: integerNumberOfImportantAppointments is an integer. How can I display this in a messagebox?

I am getting the following error: Invalid Pointer Addition.

Also, can I choose the icon for the messagebox? A question in this case.

Solution 1

Here you go. You need to use wide characters in the call to MessageBox and you need to store the result in a variable, before working out what to do next.

const int result = MessageBox(NULL, L"Test message", L"test title",  MB_YESNOCANCEL);

switch (result)
{
case IDYES:
    // Do something
    break;
case IDNO:
    // Do something
    break;
case IDCANCEL:
    // Do something
    break;
}

Update, following question edit:

// Format the message with your appointment count.
CString message;
message.Format(L"You have %d important appointments. Do you wish to view them?", integerNumberOfImportantAppointments);

// Show the message box with a question mark icon
const int result = MessageBox(NULL, message, L"test title",  MB_YESNOCANCEL | MB_ICONQUESTION);

You should read the documentation for MessageBox.

Solution 2

I have no experience with C++ Builder, but it seems that you are using ANSI strings where UNICODE (actually wide character, but let's ignore details for the moment) strings are required. Try this:

if(MessageBox(NULL, L"Test message", L"test title",  MB_YESNOCANCEL) == IDYES)

Even better, to ensure that your strings are conforming to your app settings, you can use:

if(MessageBox(NULL, _T("Test message"), _T("test title"),  MB_YESNOCANCEL) == IDYES)

This will result in wide (wchar_t*) strings being used in UNICODE builds, and narrow (char*) strings in non-UNICODE builds (see '_TCHAR maps to' part in the Project Options)

For more details, see here

Solution 3

Im not sure about how to do this in C++ Building, but you need to enable I think something like multybit characters, but you need check against the documentation with your compiler.

Comments

[user1690531]

Thanks. What is the best way to detect if the yes, no or the cancel button is pressed? Do I place the Messagebox result into a variable and then use an if statement to detect the button, or some other method?

[Zdeslav Vojkovic]

If you need to handle all 3 cases differently then yes, you should store it in a variable and use if or switch-case statement to react accordingly. Otherwise, your code is fine, but then the question is why not just have MB_YESNO.

[user1690531]

I am just thinking of other situations where I might like more than two message buttons. Do I return the variable from the messagebox into an int, or is there a specific type for messagebox returns?

[Zdeslav Vojkovic]

pressing F1 will show the documentation :). As I said, I don't use C++ Builder, so I have also looked up all of this on Google.

[Adam McKee]

I've updated my answer. Try not to ask more than one question in each post.

[user1690531]

Ok, sorry. About the CString, I have added the following with no luck: #include <atlstr.h>. What do I need to do to get CString working?

[Adam McKee]

I'm not sure, have you tried adding <cstringt.h>? Here's the documentation - msdn.microsoft.com/en-us/library/5bzxfsea.aspx

[user1690531]

I have tried both cstringt.h and atlstr.h, with no luck. I am using C++ Builder. Is there an equivalent piece of code that can work that you know of in C++ Builder.

[Remy Lebeau]

CString is a Microsoft MFC class. For C++Builder VCL, use WideString (C++Builder 2007 or earlier) or UnicodeString (C++Builder 2009 or later) instead, eg: WideString s = "You have " + IntToStr(integerNumberOfImportantAppointments) + " important appointments. Do you wish to view them?"; MessageBox(NULL, s.c_bstr(), ...); or UnicodeString s = "You have " + IntToStr(integerNumberOfImportantAppointments) + " important appointments. Do you wish to view them?"; MessageBox(NULL, s.c_str(), ...);