diff --git a/src/Neo/VM/Helper.cs b/src/Neo/Extensions/SmartContract/ContractParameterExtensions.cs
similarity index 91%
rename from src/Neo/VM/Helper.cs
rename to src/Neo/Extensions/SmartContract/ContractParameterExtensions.cs
index 8a1bc2b01b..d60b61eaf2 100644
--- a/src/Neo/VM/Helper.cs
+++ b/src/Neo/Extensions/SmartContract/ContractParameterExtensions.cs
@@ -1,6 +1,6 @@
 // Copyright (C) 2015-2024 The Neo Project.
 //
-// Helper.cs file belongs to the neo project and is free
+// ContractParameterExtensions.cs file belongs to the neo project and is free
 // software distributed under the MIT software license, see the
 // accompanying file LICENSE in the main directory of the
 // repository or http://www.opensource.org/licenses/mit-license.php
@@ -10,8 +10,6 @@
 // modifications are permitted.
 
 using Neo.Cryptography.ECC;
-using Neo.Extensions;
-using Neo.Json;
 using Neo.SmartContract;
 using Neo.VM.Types;
 using System;
@@ -20,12 +18,9 @@
 using System.Numerics;
 using Array = Neo.VM.Types.Array;
 
-namespace Neo.VM
+namespace Neo.Extensions
 {
-    /// <summary>
-    /// A helper class related to NeoVM.
-    /// </summary>
-    public static class Helper
+    public static class ContractParameterExtensions
     {
         /// <summary>
         /// Converts the <see cref="ContractParameter"/> to a <see cref="StackItem"/>.
@@ -46,7 +41,7 @@ private static StackItem ToStackItem(ContractParameter parameter, List<(StackIte
             {
                 case ContractParameterType.Array:
                     if (context is null)
-                        context = new List<(StackItem, ContractParameter)>();
+                        context = [];
                     else
                         (stackItem, _) = context.FirstOrDefault(p => ReferenceEquals(p.Item2, parameter));
                     if (stackItem is null)
@@ -57,7 +52,7 @@ private static StackItem ToStackItem(ContractParameter parameter, List<(StackIte
                     break;
                 case ContractParameterType.Map:
                     if (context is null)
-                        context = new List<(StackItem, ContractParameter)>();
+                        context = [];
                     else
                         (stackItem, _) = context.FirstOrDefault(p => ReferenceEquals(p.Item2, parameter));
                     if (stackItem is null)
diff --git a/src/Neo/Persistence/ClonedCache.cs b/src/Neo/Persistence/ClonedCache.cs
index e2629e385d..d89491e2b9 100644
--- a/src/Neo/Persistence/ClonedCache.cs
+++ b/src/Neo/Persistence/ClonedCache.cs
@@ -38,6 +38,7 @@ protected override bool ContainsInternal(StorageKey key)
             return innerCache.Contains(key);
         }
 
+        /// <inheritdoc/>
         protected override StorageItem GetInternal(StorageKey key)
         {
             return innerCache[key].Clone();
diff --git a/src/Neo/Persistence/DataCache.cs b/src/Neo/Persistence/DataCache.cs
index 37664bfa67..2f5138df9c 100644
--- a/src/Neo/Persistence/DataCache.cs
+++ b/src/Neo/Persistence/DataCache.cs
@@ -310,7 +310,8 @@ public bool Contains(StorageKey key)
         /// Reads a specified entry from the underlying storage.
         /// </summary>
         /// <param name="key">The key of the entry.</param>
-        /// <returns>The data of the entry. Or <see langword="null"/> if the entry doesn't exist.</returns>
+        /// <returns>The data of the entry. Or throw <see cref="KeyNotFoundException"/> if the entry doesn't exist.</returns>
+        /// <exception cref="KeyNotFoundException">If the entry doesn't exist.</exception>
         protected abstract StorageItem GetInternal(StorageKey key);
 
         /// <summary>
diff --git a/src/Neo/Persistence/SnapshotCache.cs b/src/Neo/Persistence/SnapshotCache.cs
index 07afdccfab..3a83ad0171 100644
--- a/src/Neo/Persistence/SnapshotCache.cs
+++ b/src/Neo/Persistence/SnapshotCache.cs
@@ -61,6 +61,7 @@ public void Dispose()
             snapshot?.Dispose();
         }
 
+        /// <inheritdoc/>
         protected override StorageItem GetInternal(StorageKey key)
         {
             byte[] value = store.TryGet(key.ToArray());