diff --git a/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientEventExtensions.cs b/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientEventExtensions.cs
index 48863d34..8c92f778 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientEventExtensions.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientEventExtensions.cs
@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Xml.Linq;
 
@@ -260,8 +260,10 @@ namespace SKIT.FlurlHttpClient.Wechat.Api
             if (callbackNonce == null) throw new ArgumentNullException(nameof(callbackNonce));
             if (callbackSignature == null) throw new ArgumentNullException(nameof(callbackSignature));
 
-            ISet<string> set = new SortedSet<string>(StringComparer.Ordinal) { client.Credentials.PushToken!, callbackTimestamp, callbackNonce };
-            string sign = Utilities.SHA1Utility.Hash(string.Concat(set));
+            List<string> lstParams = new List<string>() { client.Credentials.PushToken!, callbackTimestamp, callbackNonce };
+            lstParams.Sort(StringComparer.Ordinal);
+
+            string sign = Utilities.SHA1Utility.Hash(string.Concat(lstParams));
             return string.Equals(sign, callbackSignature, StringComparison.OrdinalIgnoreCase);
         }
 
diff --git a/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientParameterExtensions.cs b/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientParameterExtensions.cs
index 9f6639c8..deb2e19b 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientParameterExtensions.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientParameterExtensions.cs
@@ -54,13 +54,9 @@ namespace SKIT.FlurlHttpClient.Wechat.Api
             string nonce = Guid.NewGuid().ToString("N");
             string cardType = "INVOICE";
 
-            ISet<string> sortedParams = new SortedSet<string>(StringComparer.Ordinal);
-            sortedParams.Add(cardType);
-            sortedParams.Add(timestamp);
-            sortedParams.Add(client.Credentials.AppId);
-            sortedParams.Add(nonce);
-            sortedParams.Add(wxcardTicket);
-            string cardSign = Utilities.SHA1Utility.Hash(string.Join(string.Empty, sortedParams)).ToLower();
+            List<string> lstParams = new List<string>() { cardType, timestamp, client.Credentials.AppId, nonce, wxcardTicket };
+            lstParams.Sort(StringComparer.Ordinal);
+            string cardSign = Utilities.SHA1Utility.Hash(string.Join(string.Empty, lstParams)).ToLower();
 
             return new ReadOnlyDictionary<string, string>(new Dictionary<string, string>()
             {