Extending Castle DynamicProxy

using System;
using System.Reflection;
using System.Reflection.Emit;
using Castle.DynamicProxy;
using Castle.DynamicProxy.Generators;
using Castle.DynamicProxy.Generators.Emitters;
using Castle.DynamicProxy.Contributors;
using PresentationModelBase;

namespace Castle.Facilities.PresentationModelIntegration
{
    public class EntityViewEncapsulationPropertyTypeContributor : ITypeContributor
    {
        public EntityViewEncapsulationPropertyTypeContributor(string encapsulatedPropertyName, Type entityType, Type propertyReturnType, Type entityViewPresentationModelType)
        {
            _encapsulatedPropertyName = encapsulatedPropertyName;
            _entityType = entityType;           
            _propertyReturnType = propertyReturnType;
            _entityViewPresentationModelType = entityViewPresentationModelType;
        }

        private string _encapsulatedPropertyName;
        private Type _entityType;        
        private Type _propertyReturnType;
        private Type _entityViewPresentationModelType;       

        public void CollectElementsToProxy(IProxyGenerationHook hook, MetaType model)
        {
            //
        }

        public void Generate(ClassEmitter @class, ProxyGenerationOptions options)
        {
            string propertyName = _entityType.Name + _encapsulatedPropertyName;
            GenerateEncapsulationProperty(@class.TypeBuilder, propertyName);
        }

        protected virtual void GenerateEncapsulationProperty(TypeBuilder typeBuilder, string propertyName) 
        {
            var constructedPresentationModelInterface = typeof(IEntityViewPresentationModel<>).MakeGenericType(_entityType);

            var propertyBuilder = typeBuilder.DefineProperty(
                propertyName,
                PropertyAttributes.None,
                _propertyReturnType,
                Type.EmptyTypes);
            
            var getterBuilder = typeBuilder.DefineMethod(
                string.Format("get_{0}", propertyName),
                MethodAttributes.SpecialName | MethodAttributes.HideBySig | MethodAttributes.Public,
                _propertyReturnType,
                Type.EmptyTypes);
            var getterGenerator = getterBuilder.GetILGenerator();

            getterGenerator.Emit(OpCodes.Ldarg_0);
            getterGenerator.Emit(OpCodes.Call, constructedPresentationModelInterface.GetProperty("Entity").GetGetMethod());
            getterGenerator.Emit(OpCodes.Call, _entityType.GetProperty(_encapsulatedPropertyName).GetGetMethod());
            getterGenerator.Emit(OpCodes.Ret);

            var setterBuilder = typeBuilder.DefineMethod(
                string.Format("set_{0}", propertyName),
                MethodAttributes.SpecialName | MethodAttributes.HideBySig | MethodAttributes.Public,
                null,
                new Type[] { _propertyReturnType });
            var setterGenerator = setterBuilder.GetILGenerator();

            Label returnStatement = setterGenerator.DefineLabel();             
            setterGenerator.Emit(OpCodes.Ldarg_1);
            setterGenerator.Emit(OpCodes.Ldarg_0);
            setterGenerator.Emit(OpCodes.Call, constructedPresentationModelInterface.GetProperty("Entity").GetGetMethod());
            setterGenerator.Emit(OpCodes.Call, _entityType.GetProperty(_encapsulatedPropertyName).GetGetMethod());
            setterGenerator.Emit(OpCodes.Ceq);
            setterGenerator.Emit(OpCodes.Brtrue, returnStatement);            
            setterGenerator.Emit(OpCodes.Ldarg_0);           
            setterGenerator.Emit(OpCodes.Callvirt, constructedPresentationModelInterface.GetProperty("Entity").GetGetMethod());
            setterGenerator.Emit(OpCodes.Ldarg_1);
            setterGenerator.Emit(OpCodes.Call, _entityType.GetProperty(_encapsulatedPropertyName).GetSetMethod());
            setterGenerator.Emit(OpCodes.Ldarg_0);
            setterGenerator.Emit(OpCodes.Ldstr, propertyName);
            setterGenerator.Emit(OpCodes.Callvirt, _entityViewPresentationModelType.GetMethod("OnPropertyChanged", BindingFlags.NonPublic | BindingFlags.Instance));
            setterGenerator.MarkLabel(returnStatement);
            setterGenerator.Emit(OpCodes.Ret);


            propertyBuilder.SetGetMethod(getterBuilder);
            propertyBuilder.SetSetMethod(setterBuilder);
        }
    }
}