64 lines
2.1 KiB
C#
64 lines
2.1 KiB
C#
using System.Diagnostics.CodeAnalysis;
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using JNPF.DependencyInjection;
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namespace JNPF.Common.Security;
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/// <summary>
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/// 相等比较辅助类，用于快速创建<see cref="IEqualityComparer{T}"/>的实例.
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/// </summary>
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/// <example>
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/// var equalityComparer1 = EqualityHelper[Person].CreateComparer(p => p.ID);
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/// var equalityComparer2 = EqualityHelper[Person].CreateComparer(p => p.Name);
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/// var equalityComparer3 = EqualityHelper[Person].CreateComparer(p => p.Birthday.Year).
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/// </example>
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/// <typeparam name="T">要比较的类型.</typeparam>
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[SuppressSniffer]
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public static class EqualityHelper<T>
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{
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/// <summary>
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/// 创建指定对比委托<paramref name="keySelector"/>的实例.
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/// </summary>
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public static IEqualityComparer<T> CreateComparer<TV>(Func<T, TV> keySelector)
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{
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return new CommonEqualityComparer<TV>(keySelector);
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}
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/// <summary>
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/// 创建指定对比委托<paramref name="keySelector"/>与结果二次比较器<paramref name="comparer"/>的实例.
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/// </summary>
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public static IEqualityComparer<T> CreateComparer<TV>(Func<T, TV> keySelector, IEqualityComparer<TV> comparer)
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{
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return new CommonEqualityComparer<TV>(keySelector, comparer);
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}
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/// <summary>
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/// 共同平等比较器.
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/// </summary>
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/// <typeparam name="TV">要比较的类型.</typeparam>
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private class CommonEqualityComparer<TV> : IEqualityComparer<T>
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{
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private readonly IEqualityComparer<TV> _comparer;
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private readonly Func<T, TV> _keySelector;
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public CommonEqualityComparer(Func<T, TV> keySelector, IEqualityComparer<TV> comparer)
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{
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_keySelector = keySelector;
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_comparer = comparer;
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}
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public CommonEqualityComparer(Func<T, TV> keySelector)
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: this(keySelector, EqualityComparer<TV>.Default)
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{ }
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public bool Equals(T? x, T? y)
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{
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return _comparer.Equals(_keySelector(x), _keySelector(y));
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}
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public int GetHashCode([DisallowNull] T obj)
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{
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return _comparer.GetHashCode(_keySelector(obj)!);
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}
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}
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}
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