Update enum values, PropertySkip code, and add int tests

- Changed TestStatus enum to use non-sequential values (5, 10, 20, ...)
- Updated related tests and deserialization logic for new enum values
- Changed PropertySkip marker from 253 to 191 to avoid TinyInt conflicts
- PropertySkip now only written for null references, not empty values
- Improved handling of skipped enum and nullable properties in deserializer
- Enhanced compiled property setter for nullable types
- Added comprehensive int serialization tests, including edge cases
- Fixed namespace casing and added missing using directive

AyCode.Core.Tests/JsonExtensionTests.cs

@@ -1114,7 +1114,7 @@ public sealed class JsonExtensionTests
     [TestMethod]
     public void Deserialize_GenericEnum_DirectPath()
     {
-        var json = "2";
+        var json = "20";
         var result = AcJsonDeserializer.Deserialize<TestStatus>(json);
         Assert.AreEqual(TestStatus.Processing, result);
     }

AyCode.Core.Tests/Serialization/AcBinarySerializerObjectTests.cs

@@ -127,4 +127,59 @@ public class AcBinarySerializerObjectTests
         Assert.AreEqual(20, target.Child.Id);
         Assert.AreEqual("UpdatedChild", target.Child.Name);
     }
+
+    [TestMethod]
+    public void Serialize_SimpleId45_RoundTrip()
+    {
+        // Simple test to debug Id=45 serialization issue
+        var item = new TestHighReuseDto { Id = 45, CategoryCode = "test"};
+
+        var binary = item.ToBinary();
+        var result = binary.BinaryTo<TestHighReuseDto>();
+
+        Assert.IsNotNull(result);
+        Assert.AreEqual(45, result.Id, "Id should be 45 after deserialization");
+        Assert.AreEqual("test", result.CategoryCode);
+    }
+
+    [TestMethod]
+    public void Serialize_SimpleId0_RoundTrip()
+    {
+        // Test with Id=0 to see if SKIP marker is used correctly
+        var item = new TestHighReuseDto { Id = 0 };
+
+        var binary = item.ToBinary();
+        var result = binary.BinaryTo<TestHighReuseDto>();
+
+        Assert.IsNotNull(result);
+        Assert.AreEqual(0, result.Id, "Id should be 0 after deserialization");
+    }
+
+    [TestMethod]
+    [DataRow(-16, DisplayName = "TinyInt min: -16")]
+    [DataRow(-1, DisplayName = "Negative: -1")]
+    [DataRow(0, DisplayName = "Zero: 0")]
+    [DataRow(1, DisplayName = "Small: 1")]
+    [DataRow(45, DisplayName = "Was buggy: 45")]
+    [DataRow(47, DisplayName = "TinyInt max: 47")]
+    [DataRow(48, DisplayName = "Above TinyInt: 48")]
+    [DataRow(66, DisplayName = "Was PropertySkip v2: 66")]
+    [DataRow(100, DisplayName = "Medium: 100")]
+    [DataRow(191, DisplayName = "Current PropertySkip value: 191")]
+    [DataRow(192, DisplayName = "TinyInt code start: 192")]
+    [DataRow(253, DisplayName = "Was PropertySkip v1: 253")]
+    [DataRow(255, DisplayName = "Max byte: 255")]
+    [DataRow(1000, DisplayName = "Large: 1000")]
+    [DataRow(int.MaxValue, DisplayName = "MaxValue")]
+    [DataRow(int.MinValue, DisplayName = "MinValue")]
+    public void Serialize_VariousIntIds_PropertySkipTest(int id)
+    {
+        var item = new TestHighReuseDto { Id = id, CategoryCode = "test" };
+
+        var binary = item.ToBinary();
+        var result = binary.BinaryTo<TestHighReuseDto>();
+
+        Assert.IsNotNull(result);
+        Assert.AreEqual(id, result.Id, $"Id should be {id} after deserialization");
+    }
 }

AyCode.Core.Tests/Serialization/QuickBenchmark.cs

@@ -6,7 +6,7 @@ using AyCode.Core.Tests.TestModels;
 using MessagePack;
 using MessagePack.Resolvers;
 
-namespace AyCode.Core.Tests.serialization;
+namespace AyCode.Core.Tests.Serialization;
 
 [TestClass]
 public class QuickBenchmark

AyCode.Core.Tests/TestModels/AcSerializerModels.cs

@@ -1,3 +1,5 @@
+using AyCode.Core.Interfaces;
+
 namespace AyCode.Core.Tests.TestModels;
 
 /// <summary>

AyCode.Core.Tests/TestModels/SharedTestModels.cs

@@ -14,12 +14,12 @@ namespace AyCode.Core.Tests.TestModels;
 /// </summary>
 public enum TestStatus
 {
-    Pending = 0,
-    Active = 1,
-    Processing = 2,
-    Completed = 3,
-    Shipped = 4,
-    OnHold = 5
+    Pending = 5,
+    Active = 10,
+    Processing = 20,
+    Completed = 30,
+    Shipped = 40,
+    OnHold = 50
 }
 
 /// <summary>

AyCode.Core/Serializers/AcSerializerCommon.cs

@@ -480,7 +480,7 @@ public static class AcSerializerCommon
     
     /// <summary>
     /// Creates a compiled setter for a property using expression trees.
-    /// Handles nullable value types correctly.
+    /// Handles nullable value types correctly, including null values.
     /// </summary>
     public static Action<object, object?> CreateCompiledSetter(Type declaringType, PropertyInfo prop)
     {
@@ -496,9 +496,13 @@ public static class AcSerializerCommon
         
         if (underlyingType != null)
         {
-            // Nullable value type: unbox to underlying type, then convert to nullable
+            // Nullable value type: handle null case with conditional
+            // if (value == null) property = default; else property = (T?)Unbox(value)
+            var nullCheck = LExpression.Equal(valueParam, LExpression.Constant(null, typeof(object)));
+            var nullValue = LExpression.Default(propertyType);
             var unboxed = LExpression.Unbox(valueParam, underlyingType);
-            castValue = LExpression.Convert(unboxed, propertyType);
+            var converted = LExpression.Convert(unboxed, propertyType);
+            castValue = LExpression.Condition(nullCheck, nullValue, converted);
         }
         else if (propertyType.IsValueType)
         {

AyCode.Core/Serializers/Binaries/AcBinaryDeserializer.Populate.cs

@@ -1,4 +1,7 @@
+using System;
 using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
 using System.Runtime.CompilerServices;
 using AyCode.Core.Helpers;
 using static AyCode.Core.Helpers.JsonUtilities;
@@ -639,21 +642,24 @@ public static partial class AcBinaryDeserializer
             case PropertyAccessorType.Guid:
                 propInfo.SetGuid(target, default);
                 return;
+            case PropertyAccessorType.Enum:
+                propInfo.SetEnumAsInt32(target, 0);
+                return;
             case PropertyAccessorType.Object:
             default:
                 // For collections: clear instead of setting to null
-                if (propInfo.IsCollection)
-                {
-                    var collection = propInfo.GetValue(target);
-                    if (collection is IList list)
-                    {
-                        list.Clear();
-                    }
-                    // If not IList or null, leave it as-is (readonly collection or null already)
-                    return;
-                }
+                //if (propInfo.IsCollection)
+                //{
+                //    var collection = propInfo.GetValue(target);
+                //    if (collection is IList list)
+                //    {
+                //        list.Clear();
+                //    }
+                //    // If not IList or null, leave it as-is (readonly collection or null already)
+                //    return;
+                //}
 
-                // For other objects: set to null (strings, nullable types, etc.)
+                // Reference types and nullable value types: set to null
                 propInfo.SetValue(target, null);
                 return;
         }

AyCode.Core/Serializers/Binaries/AcBinarySerializer.cs

@@ -1002,7 +1002,10 @@ public static partial class AcBinarySerializer
                 {
                     // Object type - use regular getter
                     var value = prop.GetValue(obj);
-                    if (value == null || (prop.PropertyTypeCode == TypeCode.String && string.IsNullOrEmpty((string)value)))
+
+                    // SKIP marker only for null (reference types)
+                    // Empty string, empty collections, etc. are valid values and must be written!
+                    if (value == null)
                     {
                         context.WriteByte(BinaryTypeCode.PropertySkip);
                     }

AyCode.Core/Serializers/Binaries/AcBinarySerializerOptions.cs

@@ -215,7 +215,14 @@ internal static class BinaryTypeCode
     public const byte Int32TinyMax = 255;    // Upper bound for tiny int (192 + 64 - 1 = 255)
 
     // Property skip marker (for single-pass serialization optimization)
-    public const byte PropertySkip = 253;    // Marks a property with default/null value (skipped during serialization)
+    // CRITICAL: Must be in the "reserved" range 67-191 (after FixStr, before TinyInt)
+    // AND must not conflict with any other type codes.
+    // Using 191 (0xBF) - the highest value before TinyInt range starts at 192.
+    // This ensures it won't be confused with:
+    // - Primitive types (0-31)
+    // - FixStr (34-65) 
+    // - TinyInt values (192-255)
+    public const byte PropertySkip = 191;    // Marks a property with default/null value (skipped during serialization)
     
     /// <summary>
     /// Check if type code represents a reference (string or object).