空字符串 EmptyStr

XE new features 

  String sa;

    if (sa == EmptyStr)

        ShowMessage("empt");

不用再写成==""或者length()=0了


extern DELPHI_PACKAGE System::UnicodeString EmptyStr;
extern DELPHI_PACKAGE System::UnicodeString *NullStr;
extern DELPHI_PACKAGE System::WideString EmptyWideStr;
extern DELPHI_PACKAGE System::WideString *NullWideStr;
extern DELPHI_PACKAGE System::AnsiString EmptyAnsiStr;
extern DELPHI_PACKAGE System::AnsiString *NullAnsiStr;



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