Introduced basic serialization pipeline interception.

src/ExtendedXmlSerializer/ExtensionMethodsForContent.cs

@@ -94,6 +94,12 @@ public static ITypeConfiguration<T> WithMonitor<T>(this ITypeConfiguration<T> @t
 			        .Apply(Support<T>.Metadata, new SerializationMonitor<T>(monitor))
 			        .Return(@this);
 
+		public static ITypeConfiguration<T> WithInterceptor<T>(this ITypeConfiguration<T> @this,
+		                                                        ISerializationInterceptor<T> interceptor)
+			=> @this.Root.With<SerializationInterceptionExtension>()
+			        .Apply(Support<T>.Metadata, new SerializationInterceptor<T>(interceptor))
+			        .Return(@this);
+
 		/// <summary>
 		/// Allows content to be read as parameters for a constructor call to activate an object, rather than the more
 		/// traditional route of activating an object and its content read as property assignments.  This is preferred --

src/ExtendedXmlSerializer/ExtensionModel/Instances/ISerializationInterceptor.cs

@@ -0,0 +1,16 @@
+using ExtendedXmlSerializer.ContentModel.Format;
+using System;
+
+namespace ExtendedXmlSerializer.ExtensionModel.Instances
+{
+	public interface ISerializationInterceptor : ISerializationInterceptor<object> {}
+
+	public interface ISerializationInterceptor<T>
+	{
+		T Serializing(IFormatWriter writer, T instance);
+
+		T Activating(Type instanceType);
+
+		T Deserialized(IFormatReader reader, T instance);
+	}
+}

src/ExtendedXmlSerializer/ExtensionModel/Instances/SerializationInterceptionExtension.cs

@@ -0,0 +1,131 @@
+using ExtendedXmlSerializer.ContentModel;
+using ExtendedXmlSerializer.ContentModel.Content;
+using ExtendedXmlSerializer.ContentModel.Format;
+using ExtendedXmlSerializer.Core;
+using ExtendedXmlSerializer.Core.Sources;
+using ExtendedXmlSerializer.ReflectionModel;
+using JetBrains.Annotations;
+using System;
+using System.Reflection;
+
+namespace ExtendedXmlSerializer.ExtensionModel.Instances
+{
+	sealed class SerializationInterceptionExtension
+		: ISerializerExtension, IAssignable<TypeInfo, ISerializationInterceptor>
+	{
+		readonly ITypedTable<ISerializationInterceptor> _registrations;
+
+		[UsedImplicitly]
+		public SerializationInterceptionExtension() : this(new TypedTable<ISerializationInterceptor>()) {}
+
+		public SerializationInterceptionExtension(ITypedTable<ISerializationInterceptor> registrations)
+			=> _registrations = registrations;
+
+		public IServiceRepository Get(IServiceRepository parameter) => parameter.Decorate<IActivators>(Register)
+		                                                                        .Decorate<IContents>(Register);
+
+		IContents Register(IServiceProvider _, IContents previous) => new Contents(_registrations, previous);
+
+		IActivators Register(IServiceProvider _, IActivators previous) => new Activators(_registrations, previous);
+
+		void ICommand<IServices>.Execute(IServices parameter) {}
+
+		sealed class Contents : IContents
+		{
+			readonly ITypedTable<ISerializationInterceptor> _interceptors;
+			readonly IContents                              _contents;
+
+			public Contents(ITypedTable<ISerializationInterceptor> interceptors, IContents contents)
+			{
+				_interceptors = interceptors;
+				_contents     = contents;
+			}
+
+			public ISerializer Get(TypeInfo parameter)
+			{
+				var previous = _contents.Get(parameter);
+				var result   = _interceptors.IsSatisfiedBy(parameter) ? Create(parameter, previous) : previous;
+				return result;
+			}
+
+			Serializer Create(TypeInfo parameter, ISerializer previous)
+			{
+				var interceptor = _interceptors.Get(parameter);
+				var result      = new Serializer(new Reader(interceptor, previous), new Writer(interceptor, previous));
+				return result;
+			}
+		}
+
+		sealed class Activators : IActivators
+		{
+			readonly ITypedTable<ISerializationInterceptor> _table;
+			readonly IActivators                            _activators;
+
+			public Activators(ITypedTable<ISerializationInterceptor> table, IActivators activators)
+			{
+				_table      = table;
+				_activators = activators;
+			}
+
+			public IActivator Get(Type parameter)
+				=> new Activator(parameter, _activators.Get(parameter), _table.Get(parameter));
+
+			sealed class Activator : IActivator
+			{
+				readonly Type                      _instanceType;
+				readonly IActivator                _activator;
+				readonly ISerializationInterceptor _interceptor;
+
+				public Activator(Type instanceType, IActivator activator, ISerializationInterceptor interceptor)
+				{
+					_instanceType = instanceType;
+					_activator    = activator;
+					_interceptor  = interceptor;
+				}
+
+				public object Get() => _interceptor.Activating(_instanceType) ?? _activator.Get();
+			}
+		}
+
+		sealed class Writer : IWriter
+		{
+			readonly ISerializationInterceptor _interceptor;
+			readonly IWriter                   _writer;
+
+			public Writer(ISerializationInterceptor interceptor, IWriter writer)
+			{
+				_interceptor = interceptor;
+				_writer      = writer;
+			}
+
+			public void Write(IFormatWriter writer, object instance)
+			{
+				_writer.Write(writer, _interceptor.Serializing(writer, instance));
+			}
+		}
+
+		sealed class Reader : IReader
+		{
+			readonly ISerializationInterceptor _interceptor;
+			readonly IReader                   _reader;
+
+			public Reader(ISerializationInterceptor interceptor, IReader reader)
+			{
+				_interceptor = interceptor;
+				_reader      = reader;
+			}
+
+			public object Get(IFormatReader parameter)
+			{
+				var instance = _reader.Get(parameter);
+				var result   = _interceptor.Deserialized(parameter, instance);
+				return result;
+			}
+		}
+
+		public void Assign(TypeInfo key, ISerializationInterceptor value)
+		{
+			_registrations.Assign(key, value);
+		}
+	}
+}

src/ExtendedXmlSerializer/ExtensionModel/Instances/SerializationInterceptor.cs

@@ -0,0 +1,20 @@
+using ExtendedXmlSerializer.ContentModel.Format;
+using System;
+
+namespace ExtendedXmlSerializer.ExtensionModel.Instances
+{
+	sealed class SerializationInterceptor<T> : ISerializationInterceptor
+	{
+		readonly ISerializationInterceptor<T> _interceptor;
+
+		public SerializationInterceptor(ISerializationInterceptor<T> interceptor) => _interceptor = interceptor;
+
+		public object Serializing(IFormatWriter writer, object instance)
+			=> _interceptor.Serializing(writer, (T)instance);
+
+		public object Activating(Type instanceType) => _interceptor.Activating(instanceType);
+
+		public object Deserialized(IFormatReader reader, object instance)
+			=> _interceptor.Deserialized(reader, (T)instance);
+	}
+}

test/ExtendedXmlSerializer.Tests.ReportedIssues/Issue451Tests.cs

@@ -0,0 +1,62 @@
+using ExtendedXmlSerializer.Configuration;
+using ExtendedXmlSerializer.ContentModel.Format;
+using ExtendedXmlSerializer.ExtensionModel.Instances;
+using ExtendedXmlSerializer.Tests.ReportedIssues.Support;
+using FluentAssertions;
+using System;
+using Xunit;
+
+namespace ExtendedXmlSerializer.Tests.ReportedIssues
+{
+	public sealed class Issue451Tests
+	{
+		[Fact]
+		public void Verify()
+		{
+			var serializer = new ConfigurationContainer().Type<Subject>()
+			                                             .WithInterceptor(Interceptor.Default)
+			                                             .Create()
+			                                             .ForTesting();
+
+			var instance = new Subject();
+
+			instance.Count.Should().Be(0);
+			const string content =
+				@"<?xml version=""1.0"" encoding=""utf-8""?><Issue451Tests-Subject xmlns=""clr-namespace:ExtendedXmlSerializer.Tests.ReportedIssues;assembly=ExtendedXmlSerializer.Tests.ReportedIssues""><Count>1</Count></Issue451Tests-Subject>";
+			serializer.Assert(instance, content);
+			instance.Count.Should().Be(1);
+
+			var cycled = serializer.Deserialize<Subject>(content);
+			cycled.Should().BeOfType<ActivatedSubject>();
+			cycled.Count.Should().Be(2);
+		}
+
+		sealed class Interceptor : ISerializationInterceptor<Subject>
+		{
+			public static Interceptor Default { get; } = new Interceptor();
+
+			Interceptor() {}
+
+			public Subject Serializing(IFormatWriter writer, Subject instance)
+			{
+				instance.Count++;
+				return instance;
+			}
+
+			public Subject Activating(Type instanceType) => new ActivatedSubject();
+
+			public Subject Deserialized(IFormatReader reader, Subject instance)
+			{
+				instance.Count++;
+				return instance;
+			}
+		}
+
+		sealed class ActivatedSubject : Subject {}
+
+		class Subject
+		{
+			public uint Count { get; set; }
+		}
+	}
+}