From 60a0c0221d63a52e74296394432a7fc9cd1f6613 Mon Sep 17 00:00:00 2001
From: Niklas Hamann <nhamann@phoenixcontact.com>
Date: Thu, 11 Sep 2025 12:45:06 +0200
Subject: [PATCH] Fix nullable porperties serialization exception in
 `EntryConvert`

Issue:
Nullable primitive type throws exception on serialization.

Solution:
Now `EntryConvertGenerator.TransformType()` returns `EntryValueType.Exception`
if propertyType parameter is nullable primitive type.

[Port for release/6]
---
 src/Moryx/Serialization/EntryConvert/EntryConvert.cs     | 9 +++++++--
 src/Tests/Moryx.Tests/Serialization/DummyClass.cs        | 5 +++++
 .../Moryx.Tests/Serialization/SerializationTests.cs      | 8 ++++++++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/Moryx/Serialization/EntryConvert/EntryConvert.cs b/src/Moryx/Serialization/EntryConvert/EntryConvert.cs
index 06aaaa7f4..a8a666439 100644
--- a/src/Moryx/Serialization/EntryConvert/EntryConvert.cs
+++ b/src/Moryx/Serialization/EntryConvert/EntryConvert.cs
@@ -126,8 +126,13 @@ private static EntryValue CreateEntryValue(PropertyInfo property, ICustomSeriali
                 entryValue.Default = defaultAttribute.Value.ToString();
             else if (entryValue.Possible != null && entryValue.Possible.Length >= 1)
                 entryValue.Default = entryValue.Possible[0];
-            else if (property.PropertyType.IsValueType)
-                entryValue.Default = Activator.CreateInstance(property.PropertyType).ToString();
+            else if (property.PropertyType.IsValueType)
+            {
+                var underlyingType = Nullable.GetUnderlyingType(property.PropertyType);
+                entryValue.Default = underlyingType != null
+                    ? Activator.CreateInstance(underlyingType).ToString()
+                    : Activator.CreateInstance(property.PropertyType).ToString();
+            }
 
             // Value types should have the default value as current value
             if (ValueOrStringType(property.PropertyType))
diff --git a/src/Tests/Moryx.Tests/Serialization/DummyClass.cs b/src/Tests/Moryx.Tests/Serialization/DummyClass.cs
index fdef23b64..3fa6e43b1 100644
--- a/src/Tests/Moryx.Tests/Serialization/DummyClass.cs
+++ b/src/Tests/Moryx.Tests/Serialization/DummyClass.cs
@@ -53,4 +53,9 @@ public enum DummyEnum
         ValueA,
         ValueB
     }
+
+    public class NullablePropertiesClass
+    {
+        public int? Value { get; set; } = 0;
+    }
 }
diff --git a/src/Tests/Moryx.Tests/Serialization/SerializationTests.cs b/src/Tests/Moryx.Tests/Serialization/SerializationTests.cs
index 52f3e1997..e9efafdb2 100644
--- a/src/Tests/Moryx.Tests/Serialization/SerializationTests.cs
+++ b/src/Tests/Moryx.Tests/Serialization/SerializationTests.cs
@@ -847,6 +847,14 @@ public void MemoryStreamEncode()
             Assert.AreEqual("VGhpcyBpcyBhIHRlc3Q=", entry.SubEntries[0].Value.Current);
         }
 
+        [Test(Description = "Testing nullable properties")]
+        public void NullableProperty()
+        {
+            var nullablePropertiesObject = new NullablePropertiesClass();
+
+            Assert.DoesNotThrow(() => EntryConvert.EncodeObject(nullablePropertiesObject));
+        }
+
         [Test(Description = "Decodes to a MemoryStream and creates a new stream")]
         public void MemoryStreamDecode()
         {