Removed the [DataContract] attribute added on ArtifactBase in the migration from V8 to V9, which has the effect of making all properties on derived artifacts opt-in.

Handled the omission of the checksum value from the serialized string without taking a Json.Net dependency.

src/Umbraco.Core/Deploy/ArtifactBase.cs

@@ -1,22 +1,18 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Runtime.Serialization;
 
 namespace Umbraco.Cms.Core.Deploy
 {
     /// <summary>
     /// Provides a base class to all artifacts.
     /// </summary>
-    [DataContract]
     public abstract class ArtifactBase<TUdi> : IArtifact
         where TUdi : Udi
     {
         protected ArtifactBase(TUdi udi, IEnumerable<ArtifactDependency> dependencies = null)
         {
-            if (udi == null)
-                throw new ArgumentNullException("udi");
-            Udi = udi;
+            Udi = udi ?? throw new ArgumentNullException("udi");
             Name = Udi.ToString();
 
             Dependencies = dependencies ?? Enumerable.Empty<ArtifactDependency>();
@@ -24,38 +20,31 @@ namespace Umbraco.Cms.Core.Deploy
         }
 
         private readonly Lazy<string> _checksum;
+
         private IEnumerable<ArtifactDependency> _dependencies;
 
         protected abstract string GetChecksum();
 
         #region Abstract implementation of IArtifactSignature
 
-        Udi IArtifactSignature.Udi
-        {
-            get { return Udi; }
-        }
+        Udi IArtifactSignature.Udi => Udi;
 
-        [DataMember]
         public TUdi Udi { get; set; }
 
-        [IgnoreDataMember]
-        public string Checksum
-        {
-            get { return _checksum.Value; }
-        }
+        public string Checksum => _checksum.Value;
+
+        public bool ShouldSerializeChecksum() => false;
 
-        [DataMember]
         public IEnumerable<ArtifactDependency> Dependencies
         {
-            get { return _dependencies; }
-            set { _dependencies = value.OrderBy(x => x.Udi); }
+            get => _dependencies;
+            set => _dependencies = value.OrderBy(x => x.Udi);
         }
 
         #endregion
 
-        [DataMember]
         public string Name { get; set; }
-        [DataMember]
+
         public string Alias { get; set; }
     }
 }

src/Umbraco.Tests.UnitTests/Umbraco.Core/Deploy/ArtifactBaseTests.cs

@@ -0,0 +1,41 @@
+// Copyright (c) Umbraco.
+// See LICENSE for more details.
+
+using System;
+using System.Collections.Generic;
+using Newtonsoft.Json;
+using NUnit.Framework;
+using Umbraco.Cms.Core;
+using Umbraco.Cms.Core.Deploy;
+
+namespace Umbraco.Cms.Tests.UnitTests.Umbraco.Core.Deploy
+{
+    [TestFixture]
+    public class ArtifactBaseTests
+    {
+        [Test]
+        public void CanSerialize()
+        {
+            var udi = new GuidUdi("test", Guid.Parse("3382d5433b5749d08919bc9961422a1f"));
+            var artifact = new TestArtifact(udi, new List<ArtifactDependency>())
+            {
+                Name = "Test Name",
+                Alias = "testAlias",
+            };
+
+            var serialized = JsonConvert.SerializeObject(artifact);
+
+            var expected = "{\"Udi\":\"umb://test/3382d5433b5749d08919bc9961422a1f\",\"Dependencies\":[],\"Name\":\"Test Name\",\"Alias\":\"testAlias\"}";
+            Assert.AreEqual(expected, serialized);
+        }
+
+        private class TestArtifact : ArtifactBase<GuidUdi>
+        {
+            public TestArtifact(GuidUdi udi, IEnumerable<ArtifactDependency> dependencies = null) : base(udi, dependencies)
+            {
+            }
+
+            protected override string GetChecksum() => "test checksum value";
+        }
+    }
+}