SqlLinq: Taking LINQ to SQL in the Other Direction

using System;
using System.Linq;
using System.Reflection;
using System.Diagnostics;
using System.Collections.Generic;

namespace Kackman.Framework
{
    public sealed class PropertyLink : IDisposable
    {
        private object m_object1;
        private object m_object2;

        private string m_propertyName;

        public PropertyLink(object object1, object object2, string propertyName)
        {
            Debug.Assert(object1 != null);
            Debug.Assert(object2 != null);
            Debug.Assert(string.IsNullOrEmpty(propertyName) == false);

            m_object1 = object1;
            m_object2 = object2;
            m_propertyName = propertyName;

            SyncValues(m_object1, m_object2, m_propertyName);

            Bind();
        }
 
        public object Object1 { get { return m_object1; } }

        public object Object2 { get { return m_object2; } }

        public string PropertyName { get { return m_propertyName; } }

        public static IEnumerable<PropertyLink> LinkProperties(object object1, object object2, string[] propertyNames)
        {
            Debug.Assert(propertyNames != null);
            List<PropertyLink> list = new List<PropertyLink>();

            foreach (string propertyName in propertyNames)
                list.Add(new PropertyLink(object1, object2, propertyName));

            return list;
        }

        private static void SyncValues(object source, object target, string propertyName)
        {
            PropertyInfo sourceProperty = source.GetType().GetProperty(propertyName);
            Debug.Assert(sourceProperty != null);
            Debug.Assert(sourceProperty.CanRead);
            Debug.Assert(sourceProperty.CanWrite);

            PropertyInfo targetProperty = target.GetType().GetProperty(propertyName);
            Debug.Assert(targetProperty != null);
            Debug.Assert(targetProperty.CanRead);
            Debug.Assert(targetProperty.CanWrite);

            targetProperty.SetValue(target, sourceProperty.GetValue(source, null), null);
        }

        public void Bind()
        {
            Bind(m_object1, new EventHandler(Object1_PropertyChanged));
            Bind(m_object2, new EventHandler(Object2_PropertyChanged));
        }

        public void Unbind()
        {
            Unbind(m_object1, new EventHandler(Object1_PropertyChanged));
            Unbind(m_object2, new EventHandler(Object2_PropertyChanged));
        }

        public void Dispose()
        {
            Unbind();
            GC.SuppressFinalize(this);
        }

        private void Bind(object o, Delegate d)
        {
            EventInfo e = o.GetType().GetEvent(m_propertyName + "Changed");
            Debug.Assert(e != null);
            e.AddEventHandler(o, d);
        }

        private void Unbind(object o, Delegate d)
        {
            EventInfo e = o.GetType().GetEvent(m_propertyName + "Changed");
            Debug.Assert(e != null);
            e.RemoveEventHandler(o, d);
        }

        private void Object1_PropertyChanged(object sender, EventArgs args)
        {
            Unbind(m_object2, new EventHandler(Object2_PropertyChanged));

            SyncValues(m_object1, m_object2, m_propertyName);

            Bind(m_object2, new EventHandler(Object2_PropertyChanged));
        }

        private void Object2_PropertyChanged(object sender, EventArgs args)
        {
            Unbind(m_object1, new EventHandler(Object1_PropertyChanged));

            SyncValues(m_object2, m_object1, m_propertyName);

            Bind(m_object1, new EventHandler(Object1_PropertyChanged));
        }
    }
}