61 lines
2.3 KiB
C#
61 lines
2.3 KiB
C#
using System;
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using System.Collections.Generic;
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namespace Umbraco.Core
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{
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/// <summary>
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/// A custom equality comparer that excepts a delegate to do the comparison operation
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/// </summary>
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/// <typeparam name="T"></typeparam>
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public class DelegateEqualityComparer<T> : IEqualityComparer<T>
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{
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private readonly Func<T, T, bool> _equals;
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private readonly Func<T, int> _getHashcode;
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#region Implementation of IEqualityComparer<in T>
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public DelegateEqualityComparer(Func<T, T, bool> equals, Func<T, int> getHashcode)
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{
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_getHashcode = getHashcode;
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_equals = equals;
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}
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public static DelegateEqualityComparer<T> CompareMember<TMember>(Func<T, TMember> memberExpression) where TMember : IEquatable<TMember>
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{
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return new DelegateEqualityComparer<T>(
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(x, y) => memberExpression.Invoke(x).Equals((TMember)memberExpression.Invoke(y)),
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x =>
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{
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var invoked = memberExpression.Invoke(x);
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return !ReferenceEquals(invoked, default(TMember)) ? invoked.GetHashCode() : 0;
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});
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}
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/// <summary>
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/// Determines whether the specified objects are equal.
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/// </summary>
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/// <returns>
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/// true if the specified objects are equal; otherwise, false.
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/// </returns>
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/// <param name="x">The first object of type <paramref name="T"/> to compare.</param><param name="y">The second object of type <paramref name="T"/> to compare.</param>
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public bool Equals(T x, T y)
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{
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return _equals.Invoke(x, y);
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}
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/// <summary>
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/// Returns a hash code for the specified object.
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/// </summary>
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/// <returns>
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/// A hash code for the specified object.
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/// </returns>
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/// <param name="obj">The <see cref="T:System.Object"/> for which a hash code is to be returned.</param><exception cref="T:System.ArgumentNullException">The type of <paramref name="obj"/> is a reference type and <paramref name="obj"/> is null.</exception>
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public int GetHashCode(T obj)
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{
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return _getHashcode.Invoke(obj);
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}
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#endregion
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}
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}
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