Add some custom converters as a hack to get serialization/deserializa…

…tion working.

Upgrading to .NET 5.0 should fix this as it supports working with classes without default constructors
dotnet/runtime#29895

src/Examples/Shopping.Infrastructure.Tests/ShoppingCartInfrastructureTests.cs

@@ -1,13 +1,16 @@
 using System;
 using System.Linq;
 using System.Threading.Tasks;
+using DomainLib.Aggregates;
+using DomainLib.Persistence;
 using DomainLib.Persistence.EventStore;
 using DomainLib.Serialization;
 using EventStore.ClientAPI;
 using NUnit.Framework;
 using Shopping.Domain.Aggregates;
 using Shopping.Domain.Commands;
 using Shopping.Domain.Events;
+using Shopping.Infrastructure.JsonSerialization;
 
 namespace Shopping.Infrastructure.Tests
 {
@@ -32,18 +35,35 @@ public async Task PersistedRoundTripTest()
 
             var eventsToPersist = result1.AppliedEvents.Concat(result2.AppliedEvents).ToList();
 
-            var serializer = new JsonEventSerializer();
-            serializer.RegisterEventTypeMappings(initialState.EventTypeMapping);
+            var serializer = CreateJsonSerializer(initialState.EventTypeMapping);
             var repository = new EventStoreEventsRepository(EventStoreConnection, serializer);
 
             var streamName = $"shoppingCart-{result2.NewState.Id.Value}";
 
             var nextEventVersion = await repository.SaveEventsAsync(streamName, ExpectedVersion.NoStream, eventsToPersist);
-
             var expectedNextEventVersion = eventsToPersist.Count - 1;
+
             Assert.That(nextEventVersion, Is.EqualTo(expectedNextEventVersion));
 
-            var eventsFromPersistence = await repository.LoadEventsAsync<object>(streamName);
+            var eventsFromPersistence = (await repository.LoadEventsAsync<IDomainEvent>(streamName));
+            var loadedAggregate = ShoppingCart.FromEvents(eventsFromPersistence);
+
+            // Check the loaded aggregate root state.
+            Assert.That(loadedAggregate.Id, Is.EqualTo(shoppingCartId));
+            Assert.That(loadedAggregate.Items, Has.Count.EqualTo(2));
+            Assert.That(loadedAggregate.Items[0], Is.EqualTo("First Item"));
+            Assert.That(loadedAggregate.Items[1], Is.EqualTo("Second Item"));
+        }
+
+        private static IEventSerializer CreateJsonSerializer(IEventTypeMapping eventTypeMapping)
+        {
+            var serializer = new JsonEventSerializer();
+            serializer.RegisterConverter(new ShoppingCartCreatedConverter());
+            serializer.RegisterConverter(new ItemAddedToShoppingCartConverter());
+
+            serializer.RegisterEventTypeMappings(eventTypeMapping);
+
+            return serializer;
         }
 
     }

src/Examples/Shopping.Infrastructure/JsonSerialization/ItemAddedToShoppingCartConverter.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Shopping.Domain.Events;
+
+namespace Shopping.Infrastructure.JsonSerialization
+{
+    // HACK: Add a temporary manual converter. .NET Core 3.1 doesn't support constructors with parameters
+    public class ItemAddedToShoppingCartConverter : JsonConverter<ItemAddedToShoppingCart>
+    {
+        public override ItemAddedToShoppingCart Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            reader.Read(); // Id property name
+            reader.Read(); // Id property value
+            var id = reader.GetGuid();
+
+            reader.Read(); // Item property name
+            reader.Read(); // Item property value
+            var item = reader.GetString();
+
+            // Read the rest of the object. We don't need any of this
+            while (reader.Read())
+            {
+            }
+
+            return new ItemAddedToShoppingCart(id, item);
+        }
+
+        public override void Write(Utf8JsonWriter writer, ItemAddedToShoppingCart value, JsonSerializerOptions options)
+        {
+            writer.WriteStartObject();
+            writer.WriteString("Id",value.Id);
+            writer.WriteString("Item", value.Item);
+            writer.WriteEndObject();
+        }
+    }
+}

src/Examples/Shopping.Infrastructure/JsonSerialization/ShoppingCartCreatedConverter.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Shopping.Domain.Events;
+
+namespace Shopping.Infrastructure.JsonSerialization
+{
+    // HACK: Add a temporary manual converter. .NET Core 3.1 doesn't support constructors with parameters
+    public class ShoppingCartCreatedConverter : JsonConverter<ShoppingCartCreated>
+    {
+        public override ShoppingCartCreated Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            reader.Read(); // Id property name
+            reader.Read(); // Id property value
+            var id = reader.GetGuid();
+
+            // Read the rest of the object. We don't need any of this
+            while (reader.Read())
+            {
+            }
+
+            return new ShoppingCartCreated(id);
+        }
+
+        public override void Write(Utf8JsonWriter writer, ShoppingCartCreated value, JsonSerializerOptions options)
+        {
+            writer.WriteStartObject();
+            writer.WriteString("Id",value.Id);
+            writer.WriteEndObject();
+        }
+    }
+}

src/Examples/Shopping.Infrastructure/Shopping.Infrastructure.csproj

@@ -10,8 +10,4 @@
     <ProjectReference Include="..\Shopping.Domain\Shopping.Domain.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
-    <Folder Include="JsonSerialization\" />
-  </ItemGroup>
-
 </Project>