ManyToManyPropertyConstraint.cs

using LazyEntityGraph.Core.Extensions;
using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Reflection;

namespace LazyEntityGraph.Core.Constraints
{
    public class ManyToManyPropertyConstraint<THost, TProperty> : IPropertyConstraint<THost, ICollection<TProperty>>
        where THost : class
        where TProperty : class
    {
        private readonly PropertyInfo _inverse;

        public ManyToManyPropertyConstraint(PropertyInfo propInfo, PropertyInfo inverse)
        {
            PropInfo = propInfo;
            _inverse = inverse;
        }

        public void Rebind(THost host, ICollection<TProperty> nullCollection, ICollection<TProperty> collection)
        {
            var lazyCollection = collection as LazyEntityCollection<TProperty>;
            if (lazyCollection != null)
            {
                lazyCollection.ItemAdded += x => CollectionProperty.Add(x, _inverse, host);
                lazyCollection.ItemRemoved += x => CollectionProperty.Remove(x, _inverse, host);
            }

            foreach (var x in collection)
            {
                CollectionProperty.Add(x, _inverse, host);
            }
        }

        public PropertyInfo PropInfo { get; }

        #region Equality
        protected bool Equals(ManyToManyPropertyConstraint<THost, TProperty> other)
        {
            return _inverse.PropertyEquals(other._inverse) && PropInfo.PropertyEquals(other.PropInfo);
        }

        public override bool Equals(object obj)
        {
            if (ReferenceEquals(null, obj))
                return false;
            if (ReferenceEquals(this, obj))
                return true;
            if (obj.GetType() != GetType())
                return false;
            return Equals((ManyToManyPropertyConstraint<THost, TProperty>)obj);
        }

        public override int GetHashCode()
        {
            unchecked
            {
                return ((_inverse != null ? _inverse.GetHashCode() : 0) * 397) ^
                       (PropInfo != null ? PropInfo.GetHashCode() : 0);
            }
        }

        #endregion

        public override string ToString()
        {
            return $"{typeof(THost).Name}.{PropInfo.Name} *..* {typeof(TProperty).Name}.{_inverse.Name}";
        }
    }
}