要產生sign必須要先有Nonce、HASH ID、訊息內文，
Nonce、HASH ID都已經做完了，訊息內文我就先用規格書給的OrderCreate範例好了

這邊看到 要計算sign，依規則：

1.移除有空值的參數
2.移除多節點參數，如:CardParam
3.依據參數名稱將參數由A~Z排序
4.將各欄位轉成 PropertyName=Value 的格式, 並以"&"串接成字串
5.以SHA256計算出sign，需轉大寫

好多規定

以下是規格書給的內文範例，就拿它來實際跑一次流程，比較容易理解規則

{
 "ShopNo": "BA0026_001",
 "OrderNo": "C201804300001",
 "Amount": 50000,
 "CurrencyID": "TWD",
 "PayType": "C",
 "CardParam": { "AutoBilling": "Y" },
 "PrdtName": "信用卡訂單",
 "ReturnURL": "http://10.11.22.113:8803/QPay.ApiClient/Store/Return",
 "BackendURL": "http://10.11.22.113:8803/QPay.ApiClient/AutoPush/PushSuccess"
}

首先，要移除空值、多節點參數，並且排序：

{
 "Amount": 50000,
 "BackendURL": "http://10.11.22.113:8803/QPay.ApiClient/AutoPush/PushSuccess",
 "CurrencyID": "TWD",
 "OrderNo": "C201804300001",
 "PayType": "C",
 "PrdtName": "信用卡訂單",
 "ReturnURL": "http://10.11.22.113:8803/QPay.ApiClient/Store/Return",
 "ShopNo": "BA0026_001",
}

接著，轉成 PropertyName=Value 的格式，會是這樣
Amount=50000&BackendURL=http://10.11.22.113:8803/QPay.ApiClient/AutoPush/PushSuccess&CurrencyID=TWD&OrderNo=C201804300001&PayType=C&PrdtName=信用卡訂單&ReturnURL=http://10.11.22.113:8803/QPay.ApiClient/Store/Return&ShopNo=BA0026_001

然後把nonce、hash ID加在後面
Amount=50000&BackendURL=http://10.11.22.113:8803/QPay.ApiClient/AutoPush/PushSuccess&CurrencyID=TWD&OrderNo=C201804300001&PayType=C&PrdtName=信用卡訂單&ReturnURL=http://10.11.22.113:8803/QPay.ApiClient/Store/Return&ShopNo=BA0026_001NjM2NjY5MDQ3OTQwMzIuMTphZmJjODBhOTM5NzQ1NjMyNDFhZTczMjVjYzg0Mjg5ZjQxYTk2MWI2ZjNkYTA0NDdmOTRhZjU3ZTIzOWJlNDgz4DA70F5E2D800D50B43ED3B537480C64

轉成SHA256產生的值轉大寫就得到sign了
379E0EB5741139418868C95EE22BF298D656D096EF46EC76B65AD3A0A967314E

把規則搞懂之後，就來用程式實作吧!