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/* ****************************************************************************
*
* Copyright (c) Microsoft Corporation. All rights reserved.
*
* This software is subject to the Microsoft Public License (Ms-PL).
* A copy of the license can be found in the license.htm file included
* in this distribution.
*
* You must not remove this notice, or any other, from this software.
*
* ***************************************************************************/
namespace System.Web.Mvc {
using System;
using System.Linq;
using System.Threading;
internal static class DescriptorUtil {
public static TDescriptor[] LazilyFetchOrCreateDescriptors<TReflection, TDescriptor>(ref TDescriptor[] cacheLocation, Func<TReflection[]> initializer, Func<TReflection, TDescriptor> converter) {
// did we already calculate this once?
TDescriptor[] existingCache = Interlocked.CompareExchange(ref cacheLocation, null, null);
if (existingCache != null) {
return existingCache;
}
TReflection[] memberInfos = initializer();
TDescriptor[] descriptors = memberInfos.Select(converter).Where(descriptor => descriptor != null).ToArray();
TDescriptor[] updatedCache = Interlocked.CompareExchange(ref cacheLocation, descriptors, null);
return updatedCache ?? descriptors;
}
}
}
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