php-注释一段PHP代码，能翻译成C#最好

 function pinyin($s, $isfirst = false) {    static $pinyins;    $s = trim($s);    $len = strlen($s);    if($len < 3) return $s;    if(!isset($pinyins)) {        $data = '一:yi|丁:ding|丂:kao|七:qi|丄:shang|丅:xia|丆:mu|万:wan|丈:zhang|三:san|上:shang|下:xia|丌:ji|不:bu|与:yu|丏:mian|丐:gai|丑:chou|丒:chou|专:zhuan|且:qie|丕:pi|世:shi|丗:shi|丘:qiu|丙:bing|业:ye|丛:cong|东:dong|丝:si|丞:cheng|丟:diu|丠:qiu|両:liang|丢:diu|丣:you|两:liang|严:yan|並:bing|丧:sang|丨:gun|丩:jiu|个:ge|丫:ya|丬:zhuang|中:zhong|丮:ji|丯:jie|丰:feng|丱:guan|串:chuan|丳:chan|临:lin|丵:zhuo|丶:zhu|丷:ha|丸:wan|丹:dan|为:wei|主:zhu|丼:jing|丽:li|举:ju|丿:pie|乀:fu|乁:yi|乂:yi|乃:nai|乄:wu|久:jiu|乆:jiu|乇:tuo|么:me|义:yi|乊:ho|之:zhi|乌:wu|乍:zha|乎:hu|乏:fa|乐:le|乑:yin|乒:ping|乓:pang|乔:qiao|乕:hu|乖:guai|乗:cheng';        $a1 = explode('|', $data);        $pinyins = array();        foreach($a1 as $v) {            $a2 = explode(':', $v);            $pinyins[$a2[0]] = $a2[1];        }    }    $rs = '';    for($i = 0; $i < $len; $i++) {        $o = ord($s[$i]);        if($o < 0x80) {            if(($o >= 48 && $o <= 57) || ($o >= 97 && $o <= 122)) {                $rs .= $s[$i]; // 0-9 a-z            }elseif($o >= 65 && $o <= 90) {                $rs .= strtolower($s[$i]); // A-Z            }else{                $rs .= '_';            }        }else{            $z = $s[$i].$s[++$i].$s[++$i];            if(isset($pinyins[$z])) {                $rs .= $isfirst ? $pinyins[$z][0] : $pinyins[$z];            }else{                $rs .= '_';            }        }    }    return $rs;}