c++ builder XE4, 10.2 Tokyo > フォルダ文字列に不正な文字が入っているかチェックする実装

C++ Builder XE4
Rad Studio 10.2 Tokyo Update 2 (追記: 2017/12/27)

static bool DirName_hasInvalidChar(String target, String invalids)
{
    String invld;
    for(int idx = 0; idx <= invalids.Length(); idx++) {
        invld = invalids.SubString(idx + 1, 1);
        if (target.Pos(invld) > 0) {
            return true;
        }
    }
    return false;

}

static void Test_DirName_hasInvalidChar()
{
    String invalids = ".\\/:*?\"<>|";

    bool ok1 = DirName_hasInvalidChar(L"XXX", invalids);
    bool ok2 = DirName_hasInvalidChar(L"314159265358979", invalids);
    bool ng1 = DirName_hasInvalidChar(L"...", invalids);
    bool ng2 = DirName_hasInvalidChar(L"A.B.C", invalids);
    bool ng3 = DirName_hasInvalidChar(L"A\\B", invalids);
    bool ng4 = DirName_hasInvalidChar(L"A/B", invalids);
    bool ng5 = DirName_hasInvalidChar(L"A:B", invalids);
    bool ng6 = DirName_hasInvalidChar(L"A*B", invalids);
    bool ng7 = DirName_hasInvalidChar(L"A?B", invalids);
    bool ng8 = DirName_hasInvalidChar(L"A\"B", invalids);
    bool ng9 = DirName_hasInvalidChar(L"A<B", invalids);
    bool ng10 = DirName_hasInvalidChar(L"A>B", invalids);
    bool ng11 = DirName_hasInvalidChar(L"A|B", invalids);

}

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    Test_DirName_hasInvalidChar();

}