diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Extensions/WechatTenpayClientEventDecryptionExtensions.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Extensions/WechatTenpayClientEventDecryptionExtensions.cs
index 2dea504e..58892659 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Extensions/WechatTenpayClientEventDecryptionExtensions.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Extensions/WechatTenpayClientEventDecryptionExtensions.cs
@@ -1,8 +1,9 @@
 using System;
-using System.Text;
 
 namespace SKIT.FlurlHttpClient.Wechat.TenpayV2
 {
+    using SKIT.FlurlHttpClient.Primitives;
+
     /// <summary>
     /// 为 <see cref="WechatTenpayClient"/> 提供回调通知事件敏感数据解密的扩展方法。
     /// </summary>
@@ -56,11 +57,11 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayV2
 
             try
             {
-                string key = Utilities.MD5Utility.Hash(client.Credentials.MerchantSecret).ToLower();
+                string key = Utilities.MD5Utility.Hash(client.Credentials.MerchantSecret).Value!.ToLower();
                 string plainXml = Utilities.AESUtility.DecryptWithECB(
-                    encodingKey: Convert.ToBase64String(Encoding.UTF8.GetBytes(key)),
-                    encodingCipherText: webhookEvent.EncryptedRequestInfo!
-                );
+                    encodingKey: new EncodedString(key, EncodingKinds.Literal),
+                    encodingCipher: new EncodedString(webhookEvent.EncryptedRequestInfo!, EncodingKinds.Base64)
+                )!;
                 plainJson = Utilities.XmlHelper.ConvertToJson(plainXml);
             }
             catch (Exception ex)
diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Extensions/WechatTenpayClientExecuteMerchantMediaExtensions.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Extensions/WechatTenpayClientExecuteMerchantMediaExtensions.cs
index 6af28c45..e564a65c 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Extensions/WechatTenpayClientExecuteMerchantMediaExtensions.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Extensions/WechatTenpayClientExecuteMerchantMediaExtensions.cs
@@ -10,6 +10,8 @@ using Flurl.Http;
 
 namespace SKIT.FlurlHttpClient.Wechat.TenpayV2
 {
+    using SKIT.FlurlHttpClient.Primitives;
+
     public static class WechatTenpayClientExecuteMerchantMediaExtensions
     {
         /// <summary>
@@ -29,7 +31,7 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayV2
                 request.FileName = Guid.NewGuid().ToString("N").ToLower() + ".jpg";
 
             if (request.FileHash is null)
-                request.FileHash = BitConverter.ToString(Utilities.MD5Utility.Hash(request.FileBytes ?? Array.Empty<byte>())).Replace("-", string.Empty).ToLower();
+                request.FileHash = EncodedString.ToHexString(Utilities.MD5Utility.Hash(request.FileBytes ?? Array.Empty<byte>())).Value!.ToLower();
 
             IFlurlRequest flurlReq = client
                 .CreateFlurlRequest(request, HttpMethod.Post, "secapi", "mch", "uploadmedia");
diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Models/VehiclePartner/GetTransitPartnerOrderResponse.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Models/VehiclePartner/GetTransitPartnerOrderResponse.cs
index ebfecaa3..d15ff29c 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Models/VehiclePartner/GetTransitPartnerOrderResponse.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Models/VehiclePartner/GetTransitPartnerOrderResponse.cs
@@ -10,7 +10,7 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayV2.Models
     [System.Text.Json.Serialization.JsonConverter(typeof(Converters.ResponseClassSystemTextJsonConverter))]
     public class GetTransitPartnerOrderResponse : WechatTenpaySignableResponse
     {
-        public static new class Types
+        public static class Types
         {
             public class Coupon : GetTransitOrderResponse.Types.Coupon
             {
diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/AESUtility.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/AESUtility.cs
index 717094f4..18b5f965 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/AESUtility.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/AESUtility.cs
@@ -1,9 +1,10 @@
 using System;
 using System.Security.Cryptography;
-using System.Text;
 
 namespace SKIT.FlurlHttpClient.Wechat.TenpayV2.Utilities
 {
+    using SKIT.FlurlHttpClient.Primitives;
+
     /// <summary>
     /// AES 算法工具类。
     /// </summary>
@@ -20,33 +21,31 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayV2.Utilities
             if (keyBytes is null) throw new ArgumentNullException(nameof(keyBytes));
             if (cipherBytes is null) throw new ArgumentNullException(nameof(cipherBytes));
 
-            using (SymmetricAlgorithm aes = Aes.Create())
-            {
-                aes.Mode = CipherMode.ECB;
-                aes.Padding = PaddingMode.PKCS7;
-                aes.Key = keyBytes;
+            using SymmetricAlgorithm aes = Aes.Create();
+            aes.Mode = CipherMode.ECB;
+            aes.Padding = PaddingMode.PKCS7;
+            aes.Key = keyBytes;
 
-                using ICryptoTransform transform = aes.CreateDecryptor();
-                return transform.TransformFinalBlock(cipherBytes, 0, cipherBytes.Length);
-            }
+            using ICryptoTransform transform = aes.CreateDecryptor();
+            return transform.TransformFinalBlock(cipherBytes, 0, cipherBytes.Length);
         }
 
         /// <summary>
         /// 基于 ECB 模式解密数据。
         /// </summary>
-        /// <param name="encodingKey">经 Base64 编码后的 AES 密钥。</param>
-        /// <param name="encodingCipherText">经 Base64 编码后的待解密数据。</param>
-        /// <returns>解密后的文本数据。</returns>
-        public static string DecryptWithECB(string encodingKey, string encodingCipherText)
+        /// <param name="encodingKey">经过编码后的（通常为 Base64）AES 密钥。</param>
+        /// <param name="encodingCipher">经过编码后的（通常为 Base64）待解密数据。</param>
+        /// <returns>解密后的数据。</returns>
+        public static EncodedString DecryptWithECB(EncodedString encodingKey, EncodedString encodingCipher)
         {
-            if (encodingKey is null) throw new ArgumentNullException(nameof(encodingKey));
-            if (encodingCipherText is null) throw new ArgumentNullException(nameof(encodingCipherText));
+            if (encodingKey.Value is null) throw new ArgumentNullException(nameof(encodingKey));
+            if (encodingCipher.Value is null) throw new ArgumentNullException(nameof(encodingCipher));
 
             byte[] plainBytes = DecryptWithECB(
-                keyBytes: Convert.FromBase64String(encodingKey),
-                cipherBytes: Convert.FromBase64String(encodingCipherText)
+                keyBytes: EncodedString.FromString(encodingKey, fallbackEncodingKind: EncodingKinds.Base64),
+                cipherBytes: EncodedString.FromString(encodingCipher, fallbackEncodingKind: EncodingKinds.Base64)
             );
-            return Encoding.UTF8.GetString(plainBytes);
+            return EncodedString.ToLiteralString(plainBytes);
         }
     }
 }
diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/HMACUtility.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/HMACUtility.cs
index 88dca83f..b97e7c10 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/HMACUtility.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/HMACUtility.cs
@@ -1,44 +1,49 @@
 using System;
 using System.Security.Cryptography;
-using System.Text;
 
 namespace SKIT.FlurlHttpClient.Wechat.TenpayV2.Utilities
 {
+    using SKIT.FlurlHttpClient.Primitives;
+
     /// <summary>
     /// HMAC 算法工具类。
     /// </summary>
     public static class HMACUtility
     {
         /// <summary>
-        /// 获取 HMAC-SHA-256 消息认证码。
+        /// 计算 HMAC-SHA-256 哈希值。
         /// </summary>
-        /// <param name="secretBytes">密钥字节数组。</param>
-        /// <param name="msgBytes">信息字节数组。</param>
-        /// <returns>消息认证码字节数组。</returns>
-        public static byte[] HashWithSHA256(byte[] secretBytes, byte[] msgBytes)
+        /// <param name="keyBytes">密钥字节数组。</param>
+        /// <param name="msgBytes">要计算哈希值的信息字节数组。</param>
+        /// <returns>哈希值字节数组。</returns>
+        public static byte[] HashWithSHA256(byte[] keyBytes, byte[] msgBytes)
         {
-            if (secretBytes is null) throw new ArgumentNullException(nameof(secretBytes));
+            if (keyBytes is null) throw new ArgumentNullException(nameof(keyBytes));
             if (msgBytes is null) throw new ArgumentNullException(nameof(msgBytes));
 
-            using HMAC hmac = new HMACSHA256(secretBytes);
+#if NET5_0_OR_GREATER
+            return HMACSHA256.HashData(keyBytes, msgBytes);
+#else
+            using HMAC hmac = new HMACSHA256(keyBytes);
             return hmac.ComputeHash(msgBytes);
+#endif
         }
 
         /// <summary>
-        /// 获取 HMAC-SHA-256 消息认证码。
+        /// 计算 HMAC-SHA-256 哈希值。
         /// </summary>
-        /// <param name="secret">密钥。</param>
-        /// <param name="message">文本信息。</param>
-        /// <returns>消息认证码。</returns>
-        public static string HashWithSHA256(string secret, string message)
+        /// <param name="key">密钥。</param>
+        /// <param name="message">要计算哈希值的信息。</param>
+        /// <returns>经过十六进制编码的哈希值。</returns>
+        public static EncodedString HashWithSHA256(string key, string message)
         {
-            if (secret is null) throw new ArgumentNullException(nameof(secret));
+            if (key is null) throw new ArgumentNullException(nameof(key));
             if (message is null) throw new ArgumentNullException(nameof(message));
 
-            byte[] secretBytes = Encoding.UTF8.GetBytes(secret);
-            byte[] msgBytes = Encoding.UTF8.GetBytes(message);
-            byte[] hashBytes = HashWithSHA256(secretBytes, msgBytes);
-            return BitConverter.ToString(hashBytes).Replace("-", string.Empty);
+            byte[] keyBytes = EncodedString.FromLiteralString(key);
+            byte[] msgBytes = EncodedString.FromLiteralString(message);
+            byte[] hashBytes = HashWithSHA256(keyBytes, msgBytes);
+            return EncodedString.ToHexString(hashBytes);
         }
     }
 }
diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/MD5Utility.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/MD5Utility.cs
index 526fe7ea..3580d9d6 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/MD5Utility.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/MD5Utility.cs
@@ -1,39 +1,44 @@
 using System;
 using System.Security.Cryptography;
-using System.Text;
 
 namespace SKIT.FlurlHttpClient.Wechat.TenpayV2.Utilities
 {
+    using SKIT.FlurlHttpClient.Primitives;
+
     /// <summary>
     /// MD5 算法工具类。
     /// </summary>
     public static class MD5Utility
     {
         /// <summary>
-        /// 获取 MD5 信息摘要。
+        /// 计算 MD5 哈希值。
         /// </summary>
-        /// <param name="bytes">信息字节数组。</param>
-        /// <returns>信息摘要字节数组。</returns>
+        /// <param name="bytes">要计算哈希值的信息字节数组。</param>
+        /// <returns>哈希值字节数组。</returns>
         public static byte[] Hash(byte[] bytes)
         {
             if (bytes is null) throw new ArgumentNullException(nameof(bytes));
 
+#if NET5_0_OR_GREATER
+            return MD5.HashData(bytes);
+#else
             using MD5 md5 = MD5.Create();
             return md5.ComputeHash(bytes);
+#endif
         }
 
         /// <summary>
-        /// 获取 MD5 信息摘要。
+        /// 计算 MD5 哈希值。
         /// </summary>
-        /// <param name="message">文本信息。</param>
-        /// <returns>信息摘要。</returns>
-        public static string Hash(string message)
+        /// <param name="message">要计算哈希值的信息。</param>
+        /// <returns>经过十六进制编码的哈希值。</returns>
+        public static EncodedString Hash(string message)
         {
             if (message is null) throw new ArgumentNullException(nameof(message));
 
-            byte[] msgBytes = Encoding.UTF8.GetBytes(message);
+            byte[] msgBytes = EncodedString.FromLiteralString(message);
             byte[] hashBytes = Hash(msgBytes);
-            return BitConverter.ToString(hashBytes).Replace("-", string.Empty);
+            return EncodedString.ToHexString(hashBytes);
         }
     }
 }
diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/__Internal/RequestSigner.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/__Internal/RequestSigner.cs
index 95afc69a..06003af7 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/__Internal/RequestSigner.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayV2/Utilities/__Internal/RequestSigner.cs
@@ -46,12 +46,12 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayV2.Utilities
             {
                 case Constants.SignTypes.MD5:
                     {
-                        return MD5Utility.Hash(queryString).ToUpper();
+                        return MD5Utility.Hash(queryString).Value!.ToUpper();
                     }
 
                 case Constants.SignTypes.HMAC_SHA256:
                     {
-                        return HMACUtility.HashWithSHA256(secretValue, queryString).ToUpper();
+                        return HMACUtility.HashWithSHA256(secretValue, queryString).Value!.ToUpper();
                     }
 
                 default:
diff --git a/test/SKIT.FlurlHttpClient.Wechat.TenpayV2.UnitTests/TestCase_ToolsAESUtilityTests.cs b/test/SKIT.FlurlHttpClient.Wechat.TenpayV2.UnitTests/TestCase_ToolsAESUtilityTests.cs
index 636b04d9..1c6bceea 100644
--- a/test/SKIT.FlurlHttpClient.Wechat.TenpayV2.UnitTests/TestCase_ToolsAESUtilityTests.cs
+++ b/test/SKIT.FlurlHttpClient.Wechat.TenpayV2.UnitTests/TestCase_ToolsAESUtilityTests.cs
@@ -4,6 +4,8 @@ using Xunit;
 
 namespace SKIT.FlurlHttpClient.Wechat.TenpayV2.UnitTests
 {
+    using SKIT.FlurlHttpClient.Primitives;
+
     public class TestCase_ToolsAESUtilityTests
     {
         [Fact(DisplayName = "测试用例：AES-ECB 解密")]
@@ -12,7 +14,7 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayV2.UnitTests
             string key = "01234567890abcdefedcba9876543210";
             string cipherText = "l/aL5GyVfl/tw3Lww6GvCQ==";
 
-            string actualPlain = Utilities.AESUtility.DecryptWithECB(encodingKey: Convert.ToBase64String(Encoding.UTF8.GetBytes(key)), encodingCipherText: cipherText);
+            string actualPlain = Utilities.AESUtility.DecryptWithECB(encodingKey: (EncodedString)Convert.ToBase64String(Encoding.UTF8.GetBytes(key)), encodingCipher: (EncodedString)cipherText)!;
             string expectedPlain = "SKIT is great!";
 
             Assert.Equal(expectedPlain, actualPlain);