Problem about creating DLL in QtCreator

[isml]

I am creating a DLL in QtCreator, but encounter a link error:
@
testqtdll2.obj:-1: error:LNK2019: unresolved external symbol "__declspec(dllimport) public: __thiscall QString::~QString(void)" (_imp??1QString@@QAE@XZ)，the symbol is referenced in "int __cdecl Add(int,int)" (?Add@@YAHHH@Z)
testqtdll2.obj:-1: error:LNK2019: unresolved external symbol "__declspec(dllimport) public: static class QString __cdecl QObject::tr(char const *,char const *)" (_imp?tr@QObject@@SA?AVQString@@PBD0@Z)，the symbol is referenced in "int __cdecl Add(int,int)" (?Add@@YAHHH@Z)
@

Test Code:

@
#include <QObject>
#include <QString>

#include "testqtdll2.h"

int TESTQTDLL2SHARED_EXPORT Add(int a, int b)
{
QString s = QObject::tr("Just a test");
return a + b;
}
@

Qt project file:

@
QT -= gui
QT += core
CONFIG += dll
TARGET = TestQtDLL2
TEMPLATE = lib
DEFINES += TESTQTDLL2_LIBRARY
SOURCES += testqtdll2.cpp
HEADERS += testqtdll2.h
TestQtDLL2_global.h
symbian {
MMP_RULES += EXPORTUNFROZEN
TARGET.UID3 = 0xE746BF96
TARGET.CAPABILITY =
TARGET.EPOCALLOWDLLDATA = 1
addFiles.sources = TestQtDLL2.dll
addFiles.path = !:/sys/bin
DEPLOYMENT += addFiles
}
unix:!symbian {
maemo5 {
target.path = /opt/usr/lib
} else {
target.path = /usr/lib
}
INSTALLS += target
}
@

Thanks in advance

[EDIT: code formatting: please wrap in @-tags, Volker]

[isml]

Could anynone give me a help?