natsu-clr/src/System.Private.CoreLib/System/Collections/Generic/NonRandomizedStringEqualityComparer.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Runtime.Serialization;

namespace System.Collections.Generic
{
    // NonRandomizedStringEqualityComparer is the comparer used by default with the Dictionary<string,...> 
    // We use NonRandomizedStringEqualityComparer as default comparer as it doesnt use the randomized string hashing which 
    // keeps the performance not affected till we hit collision threshold and then we switch to the comparer which is using 
    // randomized string hashing.
    [Serializable] // Required for compatibility with .NET Core 2.0 as we exposed the NonRandomizedStringEqualityComparer inside the serialization blob
    // Needs to be public to support binary serialization compatibility
    public sealed class NonRandomizedStringEqualityComparer : EqualityComparer<string>
    {
        internal static new IEqualityComparer<string> Default { get; } = new NonRandomizedStringEqualityComparer();

        private NonRandomizedStringEqualityComparer() { }

        public sealed override bool Equals(string x, string y) => string.Equals(x, y);

        public sealed override int GetHashCode(string obj) => obj?.GetNonRandomizedHashCode() ?? 0;
    }
}