DOP and DVMH

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.ComponentModel;
using System.Dynamic;

namespace Pfz.DistributableObservablePoco.Common
{
	public sealed class DynamicDop:
		DynamicObject,
		IDynamicDop
	{
		private sealed class _Data
		{
			internal readonly PropertyChangedEventArgs _args;
			internal object _value;

			internal _Data(PropertyChangedEventArgs args)
			{
				_args = args;
			}
		}

		private readonly ConcurrentDictionary<string, _Data> _properties = new ConcurrentDictionary<string, _Data>();
		private readonly Func<string, _Data> _createData = (propertyName) => new _Data(new PropertyChangedEventArgs(propertyName));

		public object GetValue(string propertyName)
		{
			if (propertyName == null)
				throw new ArgumentNullException("propertyName");

			_Data data;
			_properties.TryGetValue(propertyName, out data);

			if (data == null)
				return null;

			return data._value;
		}

		public void SetValue(string propertyName, object value)
		{
			if (propertyName == null)
				throw new ArgumentNullException("propertyName");

			var handler = PropertyChanged;
			var dopHandler = DopPropertyChanged;
			_Data data;
			if (handler == null && dopHandler == null)
			{ 
				if (value != null)
				{
					data = _properties.GetOrAdd(propertyName, _createData);
					data._value = value;
				}
				else
				{
					_Data oldData;
					_properties.TryRemove(propertyName, out oldData);
				}

				return;
			}

			if (value == null)
			{
				if (!_properties.TryRemove(propertyName, out data))
					return;
			}
			else
			{
				data = _properties.GetOrAdd(propertyName, _createData);
				object oldValue = data._value;
				if (oldValue != null)
				{
					Type type = value.GetType();
					if (type == oldValue.GetType())
					{
						if (type.IsValueType)
						{
							if (object.Equals(value, oldValue))
								return;
						}
						else
						{
							if (value == oldValue)
								return;
						}
					}
				}

				data._value = value;
			}

			if (handler != null)
				handler(this, data._args);

			if (dopHandler != null)
				dopHandler(this, propertyName, value);
		}

		public IEnumerable<KeyValuePair<string, object>> EnumeratePropertiesAndValues()
		{
			foreach(var pair in _properties)
			{
				string propertyName = pair.Key;
				object value = pair.Value._value;
				yield return new KeyValuePair<string, object>(propertyName, value);
			}
		}

		public override bool TryGetMember(GetMemberBinder binder, out object result)
		{
			result = GetValue(binder.Name);
			return true;
		}
		public override bool TrySetMember(SetMemberBinder binder, object value)
		{
			SetValue(binder.Name, value);
			return true;
		}

		public event PropertyChangedEventHandler PropertyChanged;
		public event DopPropertyChangedEventHandler DopPropertyChanged;
	}
}