String timestamp = "1630905585";
String nonce = "9003323344";
String signature = "tnjIAcEISq/ClrOppv/nojeZnE/pB1wNfQC/hMTME+rQMapWzvs9v1J68ueDpVzs1RW22dNotmUVy2sM6thNFRkaOx4qQGslX6kIttwvlsJsSEIR3qrjdPdUAkbP2KDRLujspxE9X0daJ6BU+rOoJ8p4c6y1/QSOMtDJoO3EABOF4O6RFHR3N7JW8o4qcf7lOOO7D4rlAB2vw6tV8WeG+OEyJ++Q0K3V1oM5uJEIPPuJkb2qlEqVYKiYLyvIdEJ1Z5qMbC9U7rKuHdeTQPl7last/h5nd6WauzDfYPKlAjZBEPYjiDqRv6Dm+4FeNtALoy6Mg7Ruxeq1pJudfj0iKg==";
String reqBody = "{\"payOrderNo\":\"21090611012001970631000463034\",\"merchantOrderNo\":\"CH2021090613190866292\",\"orderInfo\":null,\"merchantNo\":\"822126090640003\",\"termId\":\"47781282\",\"tradeMerchantNo\":\"822126090640003\",\"tradeTermId\":\"47781282\",\"channelId\":\"10000038\",\"currency\":\"156\",\"amount\":1,\"tradeType\":\"PAY\",\"payStatus\":\"S\",\"notifyStatus\":0,\"orderCreateTime\":\"2021-09-06T05:19:43.000+00:00\",\"orderEfficientTime\":\"2021-09-06T05:19:43.000+00:00\",\"extendField\":null,\"payTime\":\"2021-09-06T05:19:43.000+00:00\",\"remark\":\"\",\"noticeNum\":1,\"sign\":null,\"notifyUrl\":null,\"notifyMode\":\"2\",\"payInfo\":\"1#1#ALIPAY#0#2021090622001432581427657317\",\"lklOrderNo\":\"2021090666210003610012\",\"crdFlg\":\"92\",\"payerId1\":\"2088702852632582\",\"payerId2\":\"rob***@126.com\",\"smCrdFlg\":\"01\",\"tradeTime\":\"20210906131943\",\"accountChannelOrderNo\":\"2021090622001432581427657317\",\"actualPayAmount\":1,\"logNo\":\"66210003610012\"}";
String preSignData = timestamp + "\n" + nonce + "\n" + reqBody + "\n";//商家特殊处理的，没有可以不需要加 \n
var sigeStr = preSignData;
var publicKeyCert = @"-----BEGIN PUBLIC KEY-----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-----END PUBLIC KEY-----".Replace("-----BEGIN CERTIFICATE-----", "").Replace("-----END CERTIFICATE-----", "")
.Replace("-----BEGIN PUBLIC KEY-----", "").Replace("-----END PUBLIC KEY-----", "").Replace("\r", "").Replace("\n", "").Trim();
byte[] bytesCerContent = Convert.FromBase64String(publicKeyCert);
X509Certificate2 x509 = new X509Certificate2(bytesCerContent);
RSACryptoServiceProvider rsaPub = (RSACryptoServiceProvider)x509.PublicKey.Key;
var rsaParam = x509.GetRSAPublicKey().ExportParameters(false);
var rsa = new RSACryptoServiceProvider();
rsa.ImportParameters(rsaParam);
byte[] messageAsByte = Encoding.GetEncoding("UTF-8").GetBytes(sigeStr);
byte[] sig256 = Convert.FromBase64String(signature);
var verify256 = rsa.VerifyData(messageAsByte, CryptoConfig.MapNameToOID("SHA256"), sig256);