//请求的待签名字符串(需升序排序处理)
string content = "app_id=201****222&biz_content={\"out_trade_no\":\"20190401144352106451724\",\"total_amount\":\"0.01\",\"subject\":\"土豪机\",\"timeout_express\":\"10m\",\"qr_code_timeout_express\":\"2m\",\"store_id\":\"hk001\"}&charset=utf-8&format=json&method=alipay.trade.precreate¬ify_url=http://notify.dengw.online/do/6e5e3bd0-c2c5-4565-bcfd-bf57ea822672&sign_type=rsa2×tamp=2019-04-01 14:43:53&version=1.0";
//私钥
string privatekey="";
//编码格式
string charset="utf-8";
//签名方式
string sign_type="rsa2";
//签名方法
string sign=alipaysignature.rsasign(content, privatekey, charset,sign_type);
system.out.println("sign:" sign);