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// -----------------------------------------------------------------------
// Copyright (c) Microsoft Corporation. All rights reserved.
// -----------------------------------------------------------------------
#if !CLR40
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using Microsoft.Internal;
namespace System
{
public class Lazy<T>
{
private T _value = default(T);
private volatile bool _isValueCreated = false;
private Func<T> _valueFactory = null;
private object _lock;
public Lazy()
: this(() => Activator.CreateInstance<T>())
{
}
public Lazy(bool isThreadSafe)
: this(() => Activator.CreateInstance<T>(), isThreadSafe)
{
}
public Lazy(Func<T> valueFactory):
this(valueFactory, true)
{
}
public Lazy(Func<T> valueFactory, bool isThreadSafe)
{
Requires.NotNull(valueFactory, "valueFactory");
if(isThreadSafe)
{
this._lock = new object();
}
this._valueFactory = valueFactory;
}
public T Value
{
get
{
if (!this._isValueCreated)
{
if(this._lock != null)
{
Monitor.Enter(this._lock);
}
try
{
T value = this._valueFactory.Invoke();
this._valueFactory = null;
Thread.MemoryBarrier();
this._value = value;
this._isValueCreated = true;
}
finally
{
if(this._lock != null)
{
Monitor.Exit(this._lock);
}
}
}
return this._value;
}
}
}
}
#endif
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