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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;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Linq.Expressions;
public class QueryableCollection<T> : ICollection<T>, IQueryable<T>, IHasIsLoaded
{
private readonly ICollection<T> _collection;
private readonly IQueryable<T> _query;
public QueryableCollection(ICollection<T> collection, IQueryable<T> query)
{
_collection = collection ?? new HashSet<T>();
_query = query;
}
public IQueryable<T> Query
{
get { return _query; }
}
public bool IsLoaded { get; set; }
public void Add(T item)
{
_collection.Add(item);
}
public void Clear()
{
LazyLoad();
_collection.Clear();
}
public bool Contains(T item)
{
LazyLoad();
return _collection.Contains(item);
}
public void CopyTo(T[] array, int arrayIndex)
{
LazyLoad();
_collection.CopyTo(array, arrayIndex);
}
public int Count
{
get { return IsLoaded ? _collection.Count : _query.Count(); }
}
public bool IsReadOnly
{
get { return _collection.IsReadOnly; }
}
public bool Remove(T item)
{
LazyLoad();
return _collection.Remove(item);
}
public IEnumerator<T> GetEnumerator()
{
LazyLoad();
return _collection.GetEnumerator();
}
public bool TestLoadInEnumerator { get; set; }
IEnumerator IEnumerable.GetEnumerator()
{
// Calling lazy load here would previously cause EF to throw--see Dev11 205813
// It no longer throws, but we still can't call Load here because DetectChanges uses
// this method to determine if there are any entities in the collection, and so calling
// load here will cause DetectChanges to lazily load the collection.
// It's generally okay not to call load here because the normal case of enumerating
// the collection is through the generic enumerator
if (TestLoadInEnumerator)
{
LazyLoad();
}
return ((IEnumerable)_collection).GetEnumerator();
}
private void LazyLoad()
{
if (!IsLoaded)
{
IsLoaded = true;
_query.Load();
}
}
Expression IQueryable.Expression
{
get { return _query.Expression; }
}
Type IQueryable.ElementType
{
get { return _query.ElementType; }
}
IQueryProvider IQueryable.Provider
{
get { return _query.Provider; }
}
}
}
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