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maryamariyanmaryamariyan
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Adding TrimExcess API to Dictionary and providing tests (#26239)
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‎src/Common/tests/System/RandomExtensions.cs‎

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// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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// See the LICENSE file in the project root for more information.
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using System;
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namespace Common.System
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{
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internal static class RandomExtensions
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{
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public static void Shuffle<T>(this Random random, T[] array)
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{
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int n = array.Length;
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while (n > 1)
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{
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int k = random.Next(n--);
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T temp = array[n];
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array[n] = array[k];
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array[k] = temp;
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}
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}
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}
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}

‎src/System.Collections/ref/System.Collections.cs‎

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public virtual void OnDeserialization(object sender) { }
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public bool Remove(TKey key) { throw null; }
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public bool Remove(TKey key, out TValue value) { throw null; }
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public void TrimExcess(int capacity) { }
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public void TrimExcess() { }
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public bool TryAdd(TKey key, TValue value) { throw null; }
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void System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<TKey, TValue>>.Add(System.Collections.Generic.KeyValuePair<TKey, TValue> keyValuePair) { }
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bool System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<TKey, TValue>>.Contains(System.Collections.Generic.KeyValuePair<TKey, TValue> keyValuePair) { throw null; }

‎src/System.Collections/tests/Generic/Dictionary/Dictionary.Generic.Tests.netcoreapp.cs‎

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// See the LICENSE file in the project root for more information.
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using System.Collections.Generic;
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using System.Linq;
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using Common.System;
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using Xunit;
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namespace System.Collections.Tests
@@ -220,5 +222,201 @@ public void EnsureCapacity_Generic_CapacityIsSetToPrimeNumberLargerOrEqualToRequ
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}
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#endregion
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#region TrimExcess
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[Fact]
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public void TrimExcess_Generic_NegativeCapacity_Throw()
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{
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var dictionary = new Dictionary<TKey, TValue>();
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AssertExtensions.Throws<ArgumentOutOfRangeException>("capacity", () => dictionary.TrimExcess(-1));
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}
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[Theory]
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[InlineData(20)]
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[InlineData(23)]
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public void TrimExcess_Generic_CapacitySmallerThanCount_Throws(int suggestedCapacity)
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{
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var dictionary = new Dictionary<TKey, TValue>();
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dictionary.Add(GetNewKey(dictionary), CreateTValue(0));
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AssertExtensions.Throws<ArgumentOutOfRangeException>("capacity", () => dictionary.TrimExcess(0));
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dictionary = new Dictionary<TKey, TValue>(suggestedCapacity);
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dictionary.Add(GetNewKey(dictionary), CreateTValue(0));
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AssertExtensions.Throws<ArgumentOutOfRangeException>("capacity", () => dictionary.TrimExcess(0));
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}
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[Fact]
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public void TrimExcess_Generic_LargeInitialCapacity_TrimReducesSize()
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{
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var dictionary = new Dictionary<TKey, TValue>(20);
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dictionary.TrimExcess(7);
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Assert.Equal(7, dictionary.EnsureCapacity(0));
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}
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[Theory]
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[InlineData(20)]
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[InlineData(23)]
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public void TrimExcess_Generic_TrimToLargerThanExistingCapacity_DoesNothing(int suggestedCapacity)
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{
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var dictionary = new Dictionary<TKey, TValue>();
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int capacity = dictionary.EnsureCapacity(0);
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dictionary.TrimExcess(suggestedCapacity);
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Assert.Equal(capacity, dictionary.EnsureCapacity(0));
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dictionary = new Dictionary<TKey, TValue>(suggestedCapacity/2);
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capacity = dictionary.EnsureCapacity(0);
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dictionary.TrimExcess(suggestedCapacity);
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Assert.Equal(capacity, dictionary.EnsureCapacity(0));
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}
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[Fact]
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public void TrimExcess_Generic_DictionaryNotInitialized_CapacityRemainsAsMinPossible()
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{
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var dictionary = new Dictionary<TKey, TValue>();
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Assert.Equal(0, dictionary.EnsureCapacity(0));
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dictionary.TrimExcess();
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Assert.Equal(0, dictionary.EnsureCapacity(0));
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}
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[Theory]
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[InlineData(1)]
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[InlineData(85)]
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[InlineData(89)]
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public void TrimExcess_Generic_ClearThenTrimNonEmptyDictionary_SetsCapacityTo3(int count)
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{
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Dictionary<TKey, TValue> dictionary = (Dictionary<TKey, TValue>)GenericIDictionaryFactory(count);
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Assert.Equal(count, dictionary.Count);
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// The smallest possible capacity size after clearing a dictionary is 3
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dictionary.Clear();
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dictionary.TrimExcess();
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Assert.Equal(3, dictionary.EnsureCapacity(0));
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}
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[Theory]
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[InlineData(85)]
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[InlineData(89)]
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public void TrimExcess_NoArguments_TrimsToAtLeastCount(int count)
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{
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var dictionary = new Dictionary<int, int>(20);
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for (int i = 0; i < count; i++)
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{
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dictionary.Add(i, 0);
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}
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dictionary.TrimExcess();
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Assert.InRange(dictionary.EnsureCapacity(0), count, int.MaxValue);
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}
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[Theory]
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[InlineData(85)]
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[InlineData(89)]
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public void TrimExcess_WithArguments_OnDictionaryWithManyElementsRemoved_TrimsToAtLeastRequested(int finalCount)
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{
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const int InitToFinalRatio = 10;
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int initialCount = InitToFinalRatio * finalCount;
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var dictionary = new Dictionary<int, int>(initialCount);
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Assert.InRange(dictionary.EnsureCapacity(0), initialCount, int.MaxValue);
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for (int i = 0; i < initialCount; i++)
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{
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dictionary.Add(i, 0);
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}
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for (int i = 0; i < initialCount - finalCount; i++)
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{
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dictionary.Remove(i);
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}
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for (int i = InitToFinalRatio; i > 0; i--)
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{
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dictionary.TrimExcess(i * finalCount);
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Assert.InRange(dictionary.EnsureCapacity(0), i * finalCount, int.MaxValue);
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}
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}
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[Theory]
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[InlineData(1000, 900, 5000, 85, 89)]
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[InlineData(1000, 400, 5000, 85, 89)]
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[InlineData(1000, 900, 500, 85, 89)]
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[InlineData(1000, 400, 500, 85, 89)]
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[InlineData(1000, 400, 500, 1, 3)]
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public void TrimExcess_NoArgument_TrimAfterEachBulkAddOrRemove_TrimsToAtLeastCount(int initialCount, int numRemove, int numAdd, int newCount, int newCapacity)
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{
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Random random = new Random(32);
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var dictionary = new Dictionary<int, int>();
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dictionary.TrimExcess();
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Assert.InRange(dictionary.EnsureCapacity(0), dictionary.Count, int.MaxValue);
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var initialKeys = new int[initialCount];
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for (int i = 0; i < initialCount; i++)
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{
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initialKeys[i] = i;
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}
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random.Shuffle(initialKeys);
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foreach (var key in initialKeys)
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{
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dictionary.Add(key, 0);
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}
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dictionary.TrimExcess();
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Assert.InRange(dictionary.EnsureCapacity(0), dictionary.Count, int.MaxValue);
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random.Shuffle(initialKeys);
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for (int i = 0; i < numRemove; i++)
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{
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dictionary.Remove(initialKeys[i]);
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}
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dictionary.TrimExcess();
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Assert.InRange(dictionary.EnsureCapacity(0), dictionary.Count, int.MaxValue);
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var moreKeys = new int[numAdd];
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for (int i = 0; i < numAdd; i++)
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{
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moreKeys[i] = i + initialCount;
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}
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random.Shuffle(moreKeys);
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foreach (var key in moreKeys)
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{
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dictionary.Add(key, 0);
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}
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int currentCount = dictionary.Count;
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dictionary.TrimExcess();
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Assert.InRange(dictionary.EnsureCapacity(0), currentCount, int.MaxValue);
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int[] existingKeys = new int[currentCount];
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Array.Copy(initialKeys, numRemove, existingKeys, 0, initialCount - numRemove);
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Array.Copy(moreKeys, 0, existingKeys, initialCount - numRemove, numAdd);
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random.Shuffle(existingKeys);
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for (int i = 0; i < currentCount - newCount; i++)
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{
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dictionary.Remove(existingKeys[i]);
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}
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dictionary.TrimExcess();
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int finalCapacity = dictionary.EnsureCapacity(0);
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Assert.InRange(finalCapacity, newCount, initialCount);
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Assert.Equal(newCapacity, finalCapacity);
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}
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[Fact]
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public void TrimExcess_DictionaryHasElementsChainedWithSameHashcode_Success()
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{
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var dictionary = new Dictionary<string, int>(7);
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for (int i = 0; i < 4; i++)
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{
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dictionary.Add(i.ToString(), 0);
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}
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var s_64bit = new string[] { "95e85f8e-67a3-4367-974f-dd24d8bb2ca2", "eb3d6fe9-de64-43a9-8f58-bddea727b1ca" };
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var s_32bit = new string[] { "25b1f130-7517-48e3-96b0-9da44e8bfe0e", "ba5a3625-bc38-4bf1-a707-a3cfe2158bae" };
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string[] chained = (Environment.Is64BitProcess ? s_64bit : s_32bit).ToArray();
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dictionary.Add(chained[0], 0);
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dictionary.Add(chained[1], 0);
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for (int i = 0; i < 4; i++)
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{
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dictionary.Remove(i.ToString());
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}
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dictionary.TrimExcess(3);
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Assert.Equal(2, dictionary.Count);
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int val;
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Assert.True(dictionary.TryGetValue(chained[0], out val));
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Assert.True(dictionary.TryGetValue(chained[1], out val));
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}
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#endregion
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}
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}

‎src/System.Collections/tests/System.Collections.Tests.csproj‎

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<Compile Include="$(CommonTestPath)\System\ObjectCloner.cs">
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<Link>Common\System\ObjectCloner.cs</Link>
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</Compile>
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<Compile Include="$(CommonTestPath)\System\RandomExtensions.cs">
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<Link>Common\System\RandomExtensions.cs</Link>
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</Compile>
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<Compile Include="$(CommonTestPath)\System\Collections\DictionaryExtensions.cs" Condition="'$(TargetGroup)'!='netcoreapp'">
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<Link>Common\System\Collections\DictionaryExtensions.cs</Link>
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</Compile>
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<EmbeddedResource Include="Resources\$(AssemblyName).rd.xml" />
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</ItemGroup>
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<Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
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</Project>
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</Project>

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