求大神，把一小段PHP或易语言代码，转成C#代码

[liang969625544]

/**
* @param $param array 要签名的参数数组
* @param $key string 用户密匙
* @return string
*/
function getSign($param, $key)
{
$signPars = "";
ksort($param);
foreach ($param as $k => $v) {
if ("sign" != $k && "" != $v) {
$signPars .= $k . "=" . $v . "&";
}
}
$signPars = trim($signPars, '&');
$signPars .= $key;
$sign = md5($signPars);
return $sign;
}

$params = [
'api_token' => 1000,
'timestamp' => '1534471761',
'gid' => 1000
];
$key = "b9f781de4c96e915ae8ba5fd9144f3aa";
$sign = $this->getSign($params, $key);
echo $sign;//打印签名结果