在MFC / C ++项目中，无法将参数1从'const wchar_t *'转换为'LPCTSTR'

Question

I get a compilation error on the line:

 MessageBox(e.getAllExceptionStr().c_str(), _T("Error initializing the sound player"));

Error   4   error C2664: 'CWnd::MessageBoxA' : cannot convert parameter 1 from 'const wchar_t *' to 'LPCTSTR'   c:\users\daniel\documents\visual studio 2012\projects\mytest1\mytest1\main1.cpp 141 1   MyTest1

I don't know how to resolve this error, I tried the following:

MessageBox((wchar_t *)(e.getAllExceptionStr().c_str()), _T("Error initializing the sound player"));
MessageBox(_T(e.getAllExceptionStr().c_str()), _T("Error initializing the sound player"));

I am using the setting "Use Multi-Byte Character Set" and I don't want to change it.

Answer 1

The easiest way is simply to use MessageBoxW instead of MessageBox .

MessageBoxW(e.getAllExceptionStr().c_str(), L"Error initializing the sound player");

The second easiest way is to create a new CString from the original; it will automatically convert to/from wide string and MBCS string as necessary.

CString msg = e.getAllExceptionStr().c_str();
MessageBox(msg, _T("Error initializing the sound player"));

Answer 2

LPCSTR = const char* . You are passing it a const wchar* , which clearly is not the same thing.

Always check that you are passing API functions the right parameters. _T("") type C-string are wide strings and can't be used with that version of MessageBox() .

Answer 3

As e.getAllExceptionStr().c_str() is returning wide string then the following will work:

MessageBoxW(e.getAllExceptionStr().c_str(), L"Error initializing the sound player");

Note the W on the end of MessageBoxW ;

Answer 4

If you want to compile in the obsolete MBCS mode, you may want to use the ATL/MFC string conversion helpers , like CW2T , eg:

MessageBox(
    CW2T(e.getAllExceptionStr().c_str()),
    _T("Error initializing the sound player")
);

It seems that your getAllExceptionStr() method returns a std::wstring , so calling .c_str() on it returns a const wchar_t* .

CW2T converts from wchar_t -string to TCHAR -string, which in your case (considering the MBCS compilation mode), is equivalent to char -string.

Note however that conversions from Unicode ( wchar_t -strings) to MBCS ( char -strings) can be lossy.