From 2c362246003045ba532d4ae55169672d9c94cf99 Mon Sep 17 00:00:00 2001
From: Thomas Edward Kingstone <Tom.Kingstone@burohappold.com>
Date: Tue, 18 Feb 2025 16:53:45 +0000
Subject: [PATCH] fixed problem with querying if a value can be set to property
 where the original value was not null

---
 Serialiser_Engine/Compute/Deserialise/IObject.cs   | 6 +++---
 Serialiser_Engine/Compute/Deserialise/Immutable.cs | 6 ++++--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/Serialiser_Engine/Compute/Deserialise/IObject.cs b/Serialiser_Engine/Compute/Deserialise/IObject.cs
index 918b2dfff..92eb1e592 100644
--- a/Serialiser_Engine/Compute/Deserialise/IObject.cs
+++ b/Serialiser_Engine/Compute/Deserialise/IObject.cs
@@ -117,7 +117,7 @@ private static IObject SetProperties(this BsonDocument doc, Type type, IObject v
                         {
                             object propertyValue = item.Value.IDeserialise(prop.PropertyType, prop.GetValue(value), version, isUpgraded);
 
-                            if (CanSetValueToProperty(prop.PropertyType, propertyValue))
+                            if (CanSetValueToProperty(prop.PropertyType, propertyValue, item.Value))
                             {
                                 prop.SetValue(value, propertyValue);
                             }
@@ -152,10 +152,10 @@ private static IObject SetProperties(this BsonDocument doc, Type type, IObject v
 
         /*******************************************/
 
-        private static bool CanSetValueToProperty(Type propType, object value)
+        private static bool CanSetValueToProperty(Type propType, object value, BsonValue bsonValue)
         {
             if (value == null)
-                return !propType.IsValueType || Nullable.GetUnderlyingType(propType) != null;
+                return (!propType.IsValueType || Nullable.GetUnderlyingType(propType) != null) && (bsonValue == null || bsonValue.IsBsonNull);
             else
                 return propType.IsAssignableFrom(value.GetType());
         }
diff --git a/Serialiser_Engine/Compute/Deserialise/Immutable.cs b/Serialiser_Engine/Compute/Deserialise/Immutable.cs
index f3b77012d..0708a62a4 100644
--- a/Serialiser_Engine/Compute/Deserialise/Immutable.cs
+++ b/Serialiser_Engine/Compute/Deserialise/Immutable.cs
@@ -70,8 +70,10 @@ private static IObject DeserialiseImmutable(this BsonValue bson, Type targetType
                     List<object> arguments = new List<object>();
                     foreach (var match in matches)
                     {
-                        object propertyValue = IDeserialise(match.Properties.First().Value, match.Parameter.ParameterType, null, version, isUpgraded);
-                        if (CanSetValueToProperty(match.Parameter.ParameterType, propertyValue))
+                        BsonValue bsonValue = match.Properties.First().Value;
+                        object propertyValue = IDeserialise(bsonValue, match.Parameter.ParameterType, null, version, isUpgraded);
+
+                        if (CanSetValueToProperty(match.Parameter.ParameterType, propertyValue, bsonValue))
                             arguments.Add(propertyValue);
                         else
                         {