Concatenate LPCTSTR for MessageBox

How do I concatenate LPCTSTRs for the MessageBox? The syntax in Java is like this

LPCTSTR str1 = "String2";
LPCTSTR str2 = "";
LPCTSTR str3 = "String1";
LPCTSTR finalMsg = "";

finalMsg = str1 + str2 + str3;

What is the syntax in C++/Win32? Thanks!

#include <windows.h>
#include <tchar.h>

int main()
{
    LPCTSTR str1 = _T("String2");
    LPCTSTR str2 = _T("");
    LPCTSTR str3 = _T("String1");

    LPTSTR finalMsg = new TCHAR[_tcslen(str1) + _tcslen(str2) + _tcslen(str3) + 1];
    _tcscpy(finalMsg, str1);
    _tcscat(finalMsg, str2);
    _tcscat(finalMsg, str3);

    MessageBox(nullptr, finalMsg, _T("Message"), MB_OK);

    delete[] finalMsg;
}

Plan-B: Use the std string classes:

#include <windows.h>
#include <tchar.h>

#include <string>

using tstring = std::basic_string<TCHAR>;

int main()
{
    tstring str1 = _T("String2");
    tstring str2 = _T("");
    tstring str3 = _T("String1");

    tstring finalMsg = str1 + str2 + str3;

    MessageBox(nullptr, finalMsg.c_str(), _T("Message"), MB_OK);
}

If you don't need to support ANSI-only versions of Windows, you can drop TCHAR and ...TSTR altogether and use std::wstring, which is a template specialization of std::basic_string for wchar_t.