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Travis Whidden
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zzzprojects#764 - Code Review Changes implemented; ThreadSafeSlidingCache Tests Added
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6 files changed

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-122
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6 files changed

+335
-122
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‎src/System.Linq.Dynamic.Core/Parser/ConstantExpressionHelper.cs

+2-1
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@@ -1,4 +1,5 @@
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using System.Linq.Expressions;
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using System.Linq.Dynamic.Core.Util;
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using System.Linq.Expressions;
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namespace System.Linq.Dynamic.Core.Parser
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{

‎src/System.Linq.Dynamic.Core/Parser/ThreadSafeSlidingCache.cs

-83
This file was deleted.

‎src/System.Linq.Dynamic.Core/Util/DateTimeUtils.cs

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@@ -0,0 +1,12 @@
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namespace System.Linq.Dynamic.Core.Util
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{
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internal interface IDateTimeUtils
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{
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DateTime UtcNow { get; }
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}
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internal class DateTimeUtils : IDateTimeUtils
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{
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public DateTime UtcNow => DateTime.UtcNow;
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}
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}

‎src/System.Linq.Dynamic.Core/Util/ThreadSafeSlidingCache.cs

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using System.Collections.Concurrent;
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using System.Linq.Dynamic.Core.Validation;
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using System.Threading.Tasks;
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namespace System.Linq.Dynamic.Core.Util
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{
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internal class ThreadSafeSlidingCache<TKey, TValue> where TKey : notnull where TValue : notnull
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{
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// ReSharper disable once StaticMemberInGenericType
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private static readonly TimeSpan _defaultCleanupFrequency = TimeSpan.FromMinutes(10);
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private readonly ConcurrentDictionary<TKey, (TValue Value, DateTime ExpirationTime)> _cache;
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private readonly TimeSpan _cleanupFrequency;
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private readonly IDateTimeUtils _dateTimeProvider;
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private readonly Func<Task> _deleteExpiredCachedItemsDelegate;
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private readonly long? _minCacheItemsBeforeCleanup;
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private DateTime _lastCleanupTime = DateTime.MinValue;
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/// <summary>
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/// Sliding Thread Safe Cache
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/// </summary>
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/// <param name="timeToLive">The length of time any object would survive before being removed</param>
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/// <param name="cleanupFrequency">Only look for expired objects over specific periods</param>
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/// <param name="minCacheItemsBeforeCleanup">
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/// If defined, only allow the cleanup process after x number of cached items have
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/// been stored
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/// </param>
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/// <param name="dateTimeProvider">
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/// Provides the Time for the Caching object. Default will be created if not supplied. Used
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/// for Testing classes
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/// </param>
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public ThreadSafeSlidingCache(
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TimeSpan timeToLive,
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TimeSpan? cleanupFrequency = null,
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long? minCacheItemsBeforeCleanup = null,
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IDateTimeUtils? dateTimeProvider = null)
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{
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_cache = new ConcurrentDictionary<TKey, (TValue, DateTime)>();
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TimeToLive = timeToLive;
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_minCacheItemsBeforeCleanup = minCacheItemsBeforeCleanup;
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_cleanupFrequency = cleanupFrequency ?? _defaultCleanupFrequency;
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_deleteExpiredCachedItemsDelegate = Cleanup;
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_dateTimeProvider = dateTimeProvider ?? new DateTimeUtils();
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}
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public TimeSpan TimeToLive { get; }
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/// <summary>
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/// Provide the number of items in the cache
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/// </summary>
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public int Count => _cache.Count;
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public void AddOrUpdate(TKey key, TValue value)
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{
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Check.NotNull(key);
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Check.NotNull(value);
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var expirationTime = _dateTimeProvider.UtcNow.Add(TimeToLive);
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_cache[key] = (value, expirationTime);
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CleanupIfNeeded();
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}
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public bool TryGetValue(TKey key, out TValue value)
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{
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Check.NotNull(key);
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CleanupIfNeeded();
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if (_cache.TryGetValue(key, out var valueAndExpiration))
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{
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if (_dateTimeProvider.UtcNow <= valueAndExpiration.ExpirationTime)
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{
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value = valueAndExpiration.Value;
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_cache[key] = (value, _dateTimeProvider.UtcNow.Add(TimeToLive));
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return true;
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}
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// Remove expired item
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_cache.TryRemove(key, out _);
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}
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value = default!;
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return false;
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}
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public bool Remove(TKey key)
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{
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Check.NotNull(key);
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var removed = _cache.TryRemove(key, out _);
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CleanupIfNeeded();
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return removed;
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}
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/// <summary>
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/// Check if cache needs to be cleaned up.
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/// If it does, span the cleanup as a Task to prevent from blocking
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/// </summary>
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private void CleanupIfNeeded()
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{
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if (_dateTimeProvider.UtcNow - _lastCleanupTime > _cleanupFrequency
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&& (_minCacheItemsBeforeCleanup == null ||
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_cache.Count >=
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_minCacheItemsBeforeCleanup) // Only cleanup if we have a minimum number of items in the cache.
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)
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{
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// Set here, so we don't have re-entry due to large collection enumeration.
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_lastCleanupTime = _dateTimeProvider.UtcNow;
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Task.Run(_deleteExpiredCachedItemsDelegate);
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}
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}
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/// <summary>
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/// Cleanup the Cache
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/// </summary>
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/// <returns></returns>
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private Task Cleanup()
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{
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foreach (var key in _cache.Keys)
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{
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if (_dateTimeProvider.UtcNow > _cache[key].ExpirationTime)
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{
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_cache.TryRemove(key, out _);
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}
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}
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return Task.CompletedTask;
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}
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}
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}

‎test/System.Linq.Dynamic.Core.Tests/Util/ConstantExpressionHelperTests.cs

+38-38
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@@ -6,43 +6,43 @@ namespace System.Linq.Dynamic.Core.Tests
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{
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public partial class EntitiesTests
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{
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[Fact]
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public async Task TestConstantExpressionLeak()
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{
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//Arrange
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PopulateTestData(1, 0);
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var populateExpression = _context.Blogs.All("BlogId > 2000");
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var expressions = ConstantExpressionHelper.Expressions;
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// Should contain
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if (!expressions.TryGetValue(2000, out _))
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{
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Assert.Fail("Cache was missing constant expression for 2000");
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}
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// wait half the expiry time
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await Task.Delay(TimeSpan.FromSeconds(ConstantExpressionHelper.Expressions.TimeToLive.TotalSeconds/2));
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if (!expressions.TryGetValue(2000, out _))
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{
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Assert.Fail("Cache was missing constant expression for 2000 (1)");
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}
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// wait another half the expiry time, plus one second
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await Task.Delay(TimeSpan.FromSeconds((ConstantExpressionHelper.Expressions.TimeToLive.TotalSeconds / 2)+1));
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if (!expressions.TryGetValue(2000, out _))
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{
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Assert.Fail("Cache was missing constant expression for 2000 (2)");
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}
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// Wait for the slide cache to expire, check on second later
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await Task.Delay(ConstantExpressionHelper.Expressions.TimeToLive.Add(TimeSpan.FromSeconds(1)));
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if (expressions.TryGetValue(2000, out _))
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{
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Assert.Fail("Expected constant to be expired 2000");
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}
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}
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//[Fact]
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//public async Task TestConstantExpressionLeak()
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//{
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// //Arrange
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// PopulateTestData(1, 0);
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// var populateExpression = _context.Blogs.All("BlogId > 2000");
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// var expressions = ConstantExpressionHelper.Expressions;
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// // Should contain
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// if (!expressions.TryGetValue(2000, out _))
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// {
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// Assert.Fail("Cache was missing constant expression for 2000");
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// }
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// // wait half the expiry time
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// await Task.Delay(TimeSpan.FromSeconds(ConstantExpressionHelper.Expressions.TimeToLive.TotalSeconds/2));
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// if (!expressions.TryGetValue(2000, out _))
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// {
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// Assert.Fail("Cache was missing constant expression for 2000 (1)");
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// }
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// // wait another half the expiry time, plus one second
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// await Task.Delay(TimeSpan.FromSeconds((ConstantExpressionHelper.Expressions.TimeToLive.TotalSeconds / 2)+1));
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// if (!expressions.TryGetValue(2000, out _))
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// {
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// Assert.Fail("Cache was missing constant expression for 2000 (2)");
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// }
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// // Wait for the slide cache to expire, check on second later
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// await Task.Delay(ConstantExpressionHelper.Expressions.TimeToLive.Add(TimeSpan.FromSeconds(1)));
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// if (expressions.TryGetValue(2000, out _))
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// {
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// Assert.Fail("Expected constant to be expired 2000");
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// }
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//}
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}
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}

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