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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
namespace LazyUnicorns
{
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.Linq;
using System.Reflection;
public abstract class CachingCollectionInitializer
{
private static readonly ConcurrentDictionary<Type, IList<Tuple<string, Func<DbCollectionEntry, object>>>> _factories
= new ConcurrentDictionary<Type, IList<Tuple<string, Func<DbCollectionEntry, object>>>>();
private static readonly MethodInfo _factoryMethodInfo
= typeof(CachingCollectionInitializer).GetMethod("CreateCollection");
public virtual Type TryGetElementType(PropertyInfo collectionProperty)
{
// We can only replace properties that are declared as ICollection<T> and have a setter.
var propertyType = collectionProperty.PropertyType;
if (propertyType.IsGenericType &&
propertyType.GetGenericTypeDefinition() == typeof(ICollection<>)
&&
collectionProperty.GetSetMethod() != null)
{
return propertyType.GetGenericArguments().Single();
}
return null;
}
public virtual void InitializeCollections(DbContext context, object entity)
{
var factories = _factories.GetOrAdd(
entity.GetType(), t =>
{
var list = new List<Tuple<string, Func<DbCollectionEntry, object>>>();
foreach (var property in t.GetProperties())
{
var collectionEntry = context.Entry(entity).Member(property.Name) as DbCollectionEntry;
if (collectionEntry != null)
{
var elementType = TryGetElementType(property);
if (elementType != null)
{
list.Add(Tuple.Create(property.Name, CreateCollectionFactory(elementType)));
}
}
}
return list;
});
foreach (var factory in factories)
{
var collectionEntry = context.Entry(entity).Collection(factory.Item1);
collectionEntry.CurrentValue = factory.Item2(collectionEntry);
}
}
public virtual Func<DbCollectionEntry, object> CreateCollectionFactory(Type elementType)
{
return (Func<DbCollectionEntry, object>)Delegate.CreateDelegate(
typeof(Func<DbCollectionEntry, object>), this,
_factoryMethodInfo.MakeGenericMethod(elementType));
}
public abstract object CreateCollection<TElement>(DbCollectionEntry collectionEntry);
}
}
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